Process and system for making cyclopentadiene and/or dicyclopentadiene

ABSTRACT

Processes and systems for making cyclopentadiene and/or dicyclopentadiene include converting acyclic C5 hydrocarbon(s) into CPD in a first reactor to obtain a product mixture, washing the product mixture with a wash oil, separating the washed product mixture in a separation sub-system such as compression train to obtain a C5-rich fraction comprising CPD, dimerizing the C5-rich fraction in a dimerization reactor to obtain a product effluent, followed by separating the product effluent to obtain a DCPD-rich fraction. Wash oil can be recovered and recycled. Multiple-stage of dimerization and separation steps can be used to obtain multiple DCPD-rich fractions of various purity and quantity. C5-rich fractions from various stages of the process may be recycled to the first reactor, or converted into mogas components after selective hydrogenation. C5-rich fractions and mogas components may be optionally separated to produce value-adding chemicals.

CROSS-REFERENCE TO RELATED APPLICATIONS

This invention claims priority to and the benefit of U.S. Ser. No.62/250,692, filed Nov. 4, 2015. This application relates to U.S. Ser.No. 62/250,678, filed Nov. 4, 2015; U.S. Ser. No. 62/250,702, filed Nov.4, 2015; and U.S. Ser. No. 62/250,708, filed Nov. 4, 2015.

FIELD OF THE INVENTION

The present invention relates to processes and systems for making cyclicC5s including cyclopentadiene and/or dicyclopentadiene. In particular,the present invention relates to processes and systems for makingcyclopentadiene and dicyclopentadiene from acyclic C5 hydrocarbons.

BACKGROUND OF THE INVENTION

Cyclopentadiene (CPD) and its dimer dicyclopentadiene (DCPD) are highlydesired raw materials used throughout the chemical industry in a widerange of products such as polymeric materials, polyester resins,synthetic rubbers, solvents, fuels, fuel additives, etc. Typically,cyclopentadiene is produced as a minor byproduct in liquid fed steamcracking (e.g., naphtha and heavier feed) processes. As steam crackingprocesses shift to using lighter feed (e.g., ethane and propane feed),less CPD is produced while demand for CPD continues to rise.Cyclopentane and cyclopentene also have high value as solvents whilecyclopentene may be used as a monomer to produce polymers and as astarting material for other high value chemicals.

Consequently, there is a need for on-purpose CPD production, i.e., CPDproduced as a primary product from a feedstock as opposed to CPDproduced as a minor byproduct. U.S. Pat. No. 5,633,421 generallydiscloses a process for dehydrogenating C2-C5 paraffins to obtaincorresponding olefins. Similarly, U.S. Pat. No. 2,982,798 generallydiscloses a process for dehydrogenating aliphatic hydrocarbonscontaining 3 to 6, inclusive, carbon atoms. However, neither U.S. Pat.No. 5,633,421 nor U.S. Pat. No. 2,982,798 discloses production of CPDfrom acyclic C5 hydrocarbons, which are desirable as feedstock becausethey are plentiful and low cost. Further, many challenges exist indesigning an on-purpose CPD production process. For example, thereaction converting C5 hydrocarbons to CPD is extremely endothermic andis favored by low pressure and high temperature but significant crackingof n-pentane and other C5 hydrocarbons can occur at relatively lowtemperature (e.g., 450° C.-500° C.). Other challenges include loss ofcatalyst activity due to coking during the production process andfurther processing is needed to remove coke from the catalyst, and theinability to use oxygen-containing gas to directly provide heat input tothe reactor without damaging the catalyst.

From the perspective of storage and shipping, DCPD is easier to handlethan CPD as a feed material for subsequent chemical syntheses. DCPD andCPD are fungible in many applications. In certain applications DCPD ispreferably used directly in lieu of CPD. For other applications whereCPD is needed, DCPD can be thermally depolymerized (aka cracked) viaretro-Diels-Alder reaction to CPD at the point of use.

Conventional processes for making CPD typically produce C5 hydrocarbonstream(s) comprising CPD at a modest concentration, acyclic diolefins atsignificant concentrations, and mono olefins. Because many of the C5species have close boiling points, form azeotropes, and are reactive atdistillation temperatures, CPD recovery from the product mixture viaconventional distillation is not industrially feasible. In conventionalrecovery schemes, CPD is recovered from other C5 hydrocarbons utilizingdimerization process(es) which causes CPD to undergo Diels-Alderreaction to produce DCPD that can easily be separated from the C5hydrocarbons by conventional distillation. Unfortunately, CPD can alsoreact with other diolefins present in the stream to produce co-dimers,which contaminate the DCPD. Furthermore, reactions involvinghigher-order oligomers also occur at moderate to high temperatures.These side reactions produce undesirable co-dimers and higher-orderoligomers, which necessitate more downstream processing steps, such asrepeated, multi-step cracking and dimerization, to produce DCPD withsufficient purity required for many applications. Such processes areexpensive, low in yield, and can be prone to fouling.

Therefore, there is a need for processes and systems for the productionof CPD and/or DCPD that address the above described challenges.

SUMMARY OF THE INVENTION

It has been found that by combining a catalytic acyclic C5 hydrocarbonconversion process where production of CPD is favored over acyclicdiolefins, and an effective separation process thereafter minimizing theDiels-Alder reactions between CPD and acyclic diolefins, CPD can beproduced at a high yield, from which high-purity DCPD can be produced.

A first aspect of the present invention relates to a process for makingCPD and/or DCPD comprising: (I) feeding a C5 feedstock comprising atleast one acyclic C5 hydrocarbon into a first reactor; (II) contactingthe at least one acyclic C5 hydrocarbon with a catalyst under conversionconditions to obtain a first reactor hydrocarbon effluent comprising: C5components including CPD and acyclic diolefins; light componentsincluding hydrogen and C1-C4 hydrocarbons; one-ring aromatics; andmultiple-ring aromatics; (III) contacting the first reactor hydrocarboneffluent with a wash oil in a washing vessel, thereby obtaining: a heavystream comprising at least a portion of the wash oil and at least aportion of the multiple-ring aromatics; and a washed first reactorhydrocarbon effluent comprising at least a portion of the lightcomponents, at least a portion of the C5 components, and, optionally, aportion of the wash oil; (IV) separating the washed first reactorhydrocarbon effluent in a first separation sub-system to obtain: a firstC5-rich fraction comprising CPD and depleted of the light components; afirst light component-rich fraction comprising hydrogen and C1-C4hydrocarbons; and an optional first recovered wash oil stream; (V)supplying the heavy stream and, optionally, at least a portion of theoptional first recovered wash oil stream to a wash oil recoverysub-system; (VI) obtaining, from the wash oil recovery sub-system: aheavy oil fraction comprising the multiple-ring aromatics; a secondrecovered wash oil stream; and an optional recovered C5-rich streamcomprising CPD; and (VII) recycling at least a portion of the secondrecovered wash oil stream, and, optionally, at least a portion of theoptional first recovered wash oil stream and/or the optional recoveredC5-rich stream comprising CPD directly or indirectly to the washingvessel.

A second aspect of the present invention relates to a system for makingCPD and/or DCPD, comprising: (A) a first reactor configured to receive aC5 feedstock comprising at least one acyclic C5 hydrocarbon, an optionalhydrogen co-feedstock and an optional C1-C4 hydrocarbon co-feedstock;(B) a catalyst loaded inside the first reactor capable of catalyzing theconversion of the C5 hydrocarbons under conversion conditions to producea first reactor hydrocarbon effluent comprising: C5 hydrocarbonsincluding CPD and acyclic diolefins; one-ring aromatics; multiple-ringaromatics; and light components including hydrogen and C1-C4hydrocarbons; (C) a washing vessel configured to receive (i) at least aportion of the first reactor hydrocarbon effluent and (ii) a wash oil,and to produce a washed first reactor hydrocarbon effluent and a heavystream comprising at least a portion of the wash oil and at least aportion of the multiple-ring aromatics; (D) a wash oil recoverysub-system configured to receive at least a portion of the heavy streamand to produce a heavy oil fraction comprising at least a portion of themultiple-ring aromatics and a second recovered wash oil stream; (E) awash oil fluid communication channel configured to recycle at least aportion of the second recovered wash oil stream directly or indirectlyto the washing vessel; (F) a fluid communication channel configured tosupply at least a portion of the washed first reactor hydrocarboneffluent to the first separation sub-system; and (G) a first separationsub-system in fluid communication with the washing vessel configured toreceive at least a portion of the washed first reactor hydrocarboneffluent and to produce (i) a first C5-rich fraction comprising CPD anddepleted of hydrogen and C1-C4 hydrocarbons, (ii) a first lightcomponent-rich fraction comprising hydrogen and C1-C4 hydrocarbons, and(iii) an optional first recovered wash oil stream.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an exemplary process and systemfor making CPD and/or DCPD of the present invention.

FIG. 2 is a schematic illustration of the details of the firstseparation sub-system in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

In the present disclosure, a process is described as comprising at leastone “step.” It should be understood that each step is an action oroperation that may be carried out once or multiple times in the process,in a continuous or discontinuous fashion. Unless specified to thecontrary or the context clearly indicates otherwise, each of the stepsin a process may be conducted sequentially in the order as they arelisted, with or without overlapping with one or more other steps, or inany other order, as the case may be. In addition, one or more or evenall steps may be conducted simultaneously with regard to the same ordifferent batch of material. For example, in a continuous process, whilea first step in a process is being conducted with respect to a rawmaterial just fed into the beginning of the process, a second step maybe carried out simultaneously with respect to an intermediate materialresulting from treating the raw materials fed into the process at anearlier time in the first step. Preferably, the steps are conducted inthe order described.

Unless otherwise indicated, all numbers indicating quantities in thepresent disclosure are to be understood as being modified by the term“about” in all instances. It should also be understood that the precisenumerical values used in the specification and claims constitutespecific embodiments. Efforts have been made to ensure the accuracy ofthe data in the examples. However, it should be understood that anymeasured data inherently contain a certain level of error due to thelimitation of the technique and/or equipment used for making themeasurement.

All numbers and references to the Periodic Table of Elements are basedon the new notation as set out in Chemical and Engineering News, 63(5),27 (1985), unless otherwise specified.

DEFINITIONS

For the purpose of this specification and appended claims, the followingterms are defined.

The term “cyclic C5” or “cC5” includes, but is not limited to,cyclopentane, cyclopentene, cyclopentadiene, and mixtures of two or morethereof. The term “cyclic C₅” or “cC₅” also includes alkylated analogsof any of the foregoing, e.g., methyl cyclopentane, methyl cyclopentene,and methyl cyclopentadiene. It should be recognized for purposes of theinvention that cyclopentadiene spontaneously dimerizes over time to formdicyclopentadiene via Diels-Alder condensation over a range ofconditions, including ambient temperature and pressure.

The term “acyclic” includes, but is not limited to, linear and branchedsaturates and non-saturates.

The term “alkyl” includes saturated hydrocarbyl groups, which can belinear, branched, cyclic, or a combination of cyclic, linear and/orbranched linear.

The term “aromatic” means a planar cyclic hydrocarbyl with conjugateddouble bonds, such as benzene. As used herein, the term aromaticencompasses compounds containing one or more aromatic rings, including,but not limited to, benzene, toluene and xylene and polynucleararomatics (PNAs) which include, but are not limited to, naphthalene,anthracene, chrysene, and their alkylated versions. The term “C6+aromatics” includes compounds based upon an aromatic ring having six ormore ring atoms, including, but not limited to, benzene, toluene andxylene and polynuclear aromatics (PNAs) which include, but are notlimited to, naphthalene, anthracene, chrysene, and their alkylatedversions.

The term “BTX” includes, but is not limited to, a mixture of benzene,toluene, and xylene (ortho and/or meta and/or para).

As used herein, the term “rich,” when used to describe a component in agiven mixture or stream produced from a predecessor mixture or stream,means that the component is present at a non-negligible concentration inthe given mixture or stream that is higher than its concentration in thepredecessor mixture or stream. Thus, a C5-rich fraction produced from apredecessor stream is a fraction comprising C5 hydrocarbons at anon-negligible concentration that is higher than the concentration of C5hydrocarbons in the predecessor stream.

As used herein, the term “depleted,” when used to describe a componentin a given mixture or stream produced from a predecessor mixture orstream, means that the component is present at a concentration (whichcan be negligible) in the given mixture or stream that is lower than itsconcentration in the predecessor mixture or stream. Thus, ahydrogen-depleted fraction produced from a predecessor stream is afraction comprising hydrogen at a concentration (which can benegligible) that is lower than the concentration of hydrogen in thepredecessor stream.

As used herein, “wt %” means percentage by weight, “vol %” meanspercentage by volume, and “mol %” means percentage by mole. All rangesexpressed herein should include both end points as two specificembodiments unless specified or indicated to the contrary.

An “upper stream” as used herein may be at the very top or the side of avessel such as a fractionation column or a reactor, with or without anadditional stream above it. Preferably, an upper stream is drawn at alocation in the vicinity of the top of the column. Preferably, an upperstream is drawn at a location above at least one feed. A “lower stream”as used herein is at a location lower than the upper stream, which maybe at the very bottom or the side of a vessel, and if at the side, withor without an additional stream below it. Preferably, a lower stream isdrawn at a location in the vicinity of the bottom of the column.Preferably, a lower stream is drawn at a location below at least onefeed. As used herein, a “middle stream” is a stream between an upperstream and a lower stream.

The term “divided-wall distillation column” means a distillation columnproducing an upper stream, a lower stream, and a middle stream from oneor more feed stream, having a dividing wall within the shellpartitioning the inner space into two sections, one comprising an inletfor receiving the feed stream, and the other comprising an outlet forejecting the middle stream. The dividing wall limits mass transferwithin the shell to areas above and below it only.

The term “light hydrocarbons” means hydrocarbons comprising 1 to 4carbon atoms in their molecule structures. The term “light components”means hydrogen and hydrocarbons comprising 1 to 4 carbon atoms in theirmolecule structures. The term “hydrogen” means molecular H₂.

The term “normal boiling point” means boiling point under a pressure of101 kilopascal. The terms “vapor” and “gas” are both inclusive to mean aphase that is entirely vapor, entirely gas and mixtures of gas andvapor.

As used herein, the term “essentially free of” means comprising at aconcentration not higher than 1 wt %, e.g., ≦0.8 wt %, ≦0.6 wt %, ≦0.5wt %, ≦0.1 wt %, ≦0.01 wt %, or even ≦0.001 wt %.

The term “mogas” means a mixture of organic compounds suitable as fuelfor use in gasoline internal combustion engine.

The term “coke” includes, but is not limited to, a low hydrogen contenthydrocarbon that is adsorbed on the catalyst composition.

The term “Cn” means hydrocarbon(s) having n carbon atom(s) per molecule,wherein n is a positive integer. Thus, a C5 hydrocarbon feedstock,therefore, comprises one or more hydrocarbon, saturated or unsaturated,having 5 carbon atoms per molecule, such as n-pentane, 2-methyl-butane,2,2-dimethylpentane, 1-pentene, 2-pentene, 2-methyl-2-butene,3-methyl-2-butene,1,3-pentadiene, 1,4-pentadiene,2-methyl-1,3-butadiene, cyclopentane, cyclopentene, and the like.

The term “Cn+” means hydrocarbon(s) having at least n carbon atom(s) permolecule.

The term “Cn−” means hydrocarbon(s) having no more than n carbon atom(s)per molecule.

The term “hydrocarbon” means a class of compounds containing hydrogenbonded to carbon, and encompasses (i) saturated hydrocarbon compounds,(ii) unsaturated hydrocarbon compounds, and (iii) mixtures ofhydrocarbon compounds (saturated and/or unsaturated), including mixturesof hydrocarbon compounds having different values of n.

The term “C5 feedstock” includes a feedstock containing n-pentane, suchas a feedstock which is predominately normal pentane (n-pentane) and/orisopentane (also referred to as methylbutane), with smaller fractions ofcyclopentane and/or neopentane (also referred to as2,2-dimethylpropane).

The term “one-ring aromatics” means aromatic compounds having onebenzene ring in the molecular structures thereof and includes alkylatedversions thereof such as toluene, xylenes, and ethylbenzene.

The term “multiple-ring aromatics” means aromatic compounds having twoor more aromatic rings in the molecular structures thereof and includesalkylated versions thereof.

The term “Group 10 metal” means an element in Group 10 of the PeriodicTable and includes Ni, Pd and Pt.

The term “Group 1 alkali metal” means an element in Group 1 of thePeriodic Table and includes, but is not limited to, Li, Na, K, Rb, Cs,and a mixture of two or more thereof, and excludes hydrogen.

The term “Group 2 alkaline earth metal” means an element in Group 2 ofthe Periodic Table and includes, but is not limited to, Be, Mg, Ca, Sr,Ba, and a mixture of two or more thereof.

The term “Group 11 metal” means an element in Group 11 of the PeriodicTable and includes, but is not limited to, Cu, Ag, Au, and a mixture oftwo or more thereof.

The term “constraint index” is defined in U.S. Pat. No. 3,972,832 andU.S. Pat. No. 4,016,218, both of which are incorporated herein byreference.

As used herein, the term “molecular sieve of the MCM-22 family” (or“material of the MCM-22 family” or “MCM-22 family material” or “MCM-22family zeolite”) includes one or more of:

molecular sieves made from a common first degree crystalline buildingblock unit cell, which unit cell has the MWW framework topology. (A unitcell is a spatial arrangement of atoms which if tiled inthree-dimensional space describes the crystal structure). Such crystalstructures are discussed in the “Atlas of Zeolite Framework Types”,Fifth edition, 2001, the entire content of which is incorporated asreference);

molecular sieves made from a common second degree building block, beinga 2-dimensional tiling of such MWW framework topology unit cells,forming a monolayer of one unit cell thickness, preferably one c-unitcell thickness;

molecular sieves made from common second degree building blocks, beinglayers of one or more than one unit cell thickness, wherein the layer ofmore than one unit cell thickness is made from stacking, packing, orbinding at least two monolayers of one unit cell thickness. The stackingof such second degree building blocks may be in a regular fashion, anirregular fashion, a random fashion, or any combination thereof; and

molecular sieves made by any regular or random 2-dimensional or3-dimensional combination of unit cells having the MWW frameworktopology.

The MCM-22 family includes those molecular sieves having an X-raydiffraction pattern including d-spacing maxima at 12.4±0.25, 6.9±0.15,3.57±0.07 and 3.42±0.07 Angstrom. The X-ray diffraction data used tocharacterize the material are obtained by standard techniques using theK-alpha doublet of copper as incident radiation and a diffractometerequipped with a scintillation counter and associated computer as thecollection system.

As used herein, the term “molecular sieve” is used synonymously with theterm “microporous crystalline material”.

As used herein, the term “carbon selectivity” means the moles of carbonin the respective cyclic C5, CPD, C1, and C2-4 formed divided by totalmoles of carbon in the C5 feedstock converted. The term “carbonselectivity to cyclic C5 of at least 30%” means that 30 moles of carbonin the cyclic C5 is formed per 100 moles of carbon in the C5 feedstock(such as n-pentane) converted.

As used herein, the term “conversion” means the moles of carbon in theacyclic C5 hydrocarbon(s) that is converted to a product. The term“conversion of at least 70% of said acyclic C5 hydrocarbon(s) to aproduct” means that at least 70% of the moles of said acyclic C5hydrocarbon(s) was converted to a product.

As used herein, the term “ferrosilicate” means an iron-containingmicroporous crystalline structure that contains iron in the frameworkstructure and/or in the channel system.

The term “alkylated naphthalene(s)” includes monoalkyl, dialkyl,trialkyl, and tetraalkyl naphthalenes.

The C5 Feedstock

A C5 feedstock comprising acyclic C5 hydrocarbon(s) useful herein isobtainable from crude oil or natural gas condensate, can include virginC5, and can include cracked C5 (in various degrees of unsaturation:alkenes, dialkenes, alkynes) produced by refining and chemicalprocesses, such as fluid catalytic cracking (FCC), reforming,hydrocracking, hydrotreating, coking, and steam cracking.

In one or more embodiments, the C5 feedstock useful in the process ofthis invention comprises pentane, pentene, pentadiene and mixtures oftwo or more thereof. Preferably, in one or more embodiments, the C5feedstock comprises at least about 50 wt %, or 60 wt %, or 75 wt %, or90 wt % saturated acyclic C5 hydrocarbon(s), ideally n-pentane, or inthe range from about 50 wt % to about 100 wt % saturated acyclic C5hydrocarbon(s), ideally n-pentane. Preferably, 2-methylbutane is presentat less than 10 wt %.

The C5 feedstock optionally does not comprise C6 aromatic compounds,such as benzene. Preferably C6 aromatic compounds are present at lessthan 5 wt %, or less than 1 wt %, or less than 0.01 wt %, or even 0 wt%.

The C5 feedstock optionally does not comprise toluene and/or one or moreof the xylenes (ortho, meta and para). Preferably, toluene and xylenes(ortho, meta and para) are present in the C5 feedstock at less than 5 wt%, preferably less than 1 wt %, preferably present at less than 0.01 wt%, preferably at 0 wt %.

The C5 feedstock optionally does not comprise C6+ aromatic compounds,preferably C6+ aromatic compounds are present at less than 5 wt %,preferably less than 1 wt %, preferably present at less than 0.01 wt %,preferably at 0 wt %.

The C5 feedstock optionally does not comprise C6+ compounds, preferablyC6+ compounds are present at less than 5 wt %, preferably less than 1 wt%, preferably present at less than 0.01 wt %, preferably at 0 wt %,preferably any C6+ aromatic compounds are present at less than 5 wt %,preferably less than 1 wt %, preferably present at less than 0.01 wt %,preferably at 0 wt %.

In the present invention, the acyclic C5 hydrocarbon(s) contained in theC5 feedstock is fed into a first reactor loaded with a catalyst, wherethe acyclic C5 hydrocarbons contact the catalyst under conversionconditions, whereupon at least a portion of the acyclic C5hydrocarbon(s) molecules are converted into CPD molecules, and areaction product containing CPD and, optionally, other cyclichydrocarbons (e.g., C5 cyclic hydrocarbons such as cyclopentane andcyclopentene) exits the first reactor as a first reactor hydrocarboneffluent. Preferably, a hydrogen co-feedstock comprising hydrogen and,optionally, light hydrocarbons, such as C1-C4 hydrocarbons, is also fedinto the first reactor. Preferably, at least a portion of the hydrogenco-feedstock is admixed with at least a portion, preferably theentirety, of the C5 feedstock prior to being fed into the first reactor.The presence of hydrogen in the feed mixture at the inlet location,where the feed first comes into contact with the catalyst, prevents orreduces the formation of coke on the catalyst particles. The catalystcomposition, which is described in greater detail below, may comprise amicroporous crystalline metallosilicate, preferably having a constraintindex in the range of less than 12, a Group 10 metal in combination witha Group 1 alkali metal and/or a Group 2 alkaline earth metal; and,optionally, a Group 11 metal. The catalyst can be made by using a methoddescribed in greater detail below.

The first reactor can be a plug flow reactor or other reactorconfigurations. The catalyst can be loaded as a fixed bed, a catalystparticle fluid, and the like. As used herein, the term “reactor” refersto any vessel(s) in which a chemical reaction occurs. Reactor includesboth distinct reactors as well as reaction zones within a single reactorapparatus and as applicable, reaction zones across multiple reactors. Inother words and as is common, a single reactor may have multiplereaction zones. Where the description refers to a first and secondreactor, the person of ordinary skill in the art will readily recognizesuch reference includes two reactors as well as a single reactor havingfirst and second reaction zones. Likewise, a first reactor hydrocarboneffluent and a second reactor effluent will be recognized to include theeffluent from the first reaction zone and the second reaction zone of asingle reactor, respectively.

As used herein, the term “moving bed” reactor refers to a zone or vesselwith contacting of solids (e.g., catalyst particles) and gas flows suchthat the superficial gas velocity (U) is below the velocity required fordilute-phase pneumatic conveying of solid particles in order to maintaina solids bed with void fraction below 95%. In a moving bed reactor, thesolids (e.g., catalyst material) may slowly travel through the reactorand may be removed from the bottom of the reactor and added to the topof the reactor. A moving bed reactor may operate under several flowregimes including settling or moving packed-bed regime (U<U_(mf)),bubbling regime (U_(mf)<U<U_(mb)), slugging regime (U_(mb)<U<U_(c)),transition to and turbulent fluidization regime (U_(c)<U<U_(tr)), andfast-fluidization regime (U>U_(tr)), where U_(mf) is minimum fluidizingvelocity, U_(mb) is minimum bubbling velocity, U_(c) is the velocity atwhich fluctuation in pressure peaks, and U_(tr) is transport velocity.These different fluidization regimes have been described in, forexample, Kunii, D., Levenspiel, O., Chapter 3 of FluidizationEngineering, 2^(nd) Edition, Butterworth-Heinemann, Boston, 1991 andWalas, S. M., Chapter 6 of Chemical Process Equipment, Revised 2^(nd)Edition, Butterworth-Heinemann, Boston, 2010, which are incorporated byreference herein.

As used herein, the term “settling bed” reactor refers to a zone orvessel wherein particulates contact with gas flows such that thesuperficial gas velocity (U) is below the minimum velocity required tofluidize the solid particles (e.g., catalyst particles), the minimumfluidization velocity (U_(mf)), U<U_(mf), in at least a portion of thereaction zone, and/or operating at a velocity higher than the minimumfluidization velocity while maintaining a gradient in gas and/or solidproperty (such as, temperature, gas or solid composition, etc.) axiallyup the reactor bed by using reactor internals to minimize gas-solidback-mixing. Description of the minimum fluidization velocity is givenin, for example, Kunii, D., Levenspiel, O., Chapter 3 of FluidizationEngineering, 2^(nd) Edition, Butterworth-Heinemann, Boston, 1991 andWalas, S. M., Chapter 6 of Chemical Process Equipment, Revised 2^(nd)Edition, Butterworth-Heinemann, Boston, 2010. A settling bed reactor maybe a “circulating settling bed reactor,” which refers to a settling bedwith a movement of solids (e.g., catalyst material) through the reactorand at least a partial recirculation of the solids (e.g., catalystmaterial). For example, the solids (e.g., catalyst material) may havebeen removed from the reactor, regenerated, reheated and/or separatedfrom the product stream and then returned back to the reactor.

As used herein, the term “fluidized bed” reactor refers to a zone orvessel with contacting of solids (e.g., catalyst particles) and gasflows such that the superficial gas velocity (U) is sufficient tofluidize solid particles (i.e., above the minimum fluidization velocityU_(mf)) and is below the velocity required for dilute-phase pneumaticconveying of solid particles in order to maintain a solids bed with voidfraction below 95%. As used herein the term “cascaded fluid-beds” meansa series arrangement of individual fluid-beds such that there can be agradient in gas and/or solid property (such as, temperature, gas orsolid composition, pressure, etc.) as the solid or gas cascades from onefluid-bed to another. Locus of minimum fluidization velocity is givenin, for example, Kunii, D., Levenspiel, O., Chapter 3 of FluidizationEngineering, 2^(nd) Edition, Butterworth-Heinemann, Boston, 1991 andWalas, S. M., Chapter 6 of Chemical Process Equipment, Revised 2^(nd)Edition, Butterworth-Heinemann, Boston, 2010. A fluidized bed reactormay be a moving fluidized bed reactor, such as a “circulating fluidizedbed reactor,” which refers to a fluidized bed with a movement of solids(e.g., catalyst material) through the reactor and at least a partialrecirculation of the solids (e.g., catalyst material). For example, thesolids (e.g., catalyst material) may have been removed from the reactor,regenerated, reheated and/or separated from the product stream and thenreturned back to the reactor.

As used herein the term “riser” reactor (also known as a transportreactor) refers to a zone or vessel (such as, vertical cylindrical pipe)used for net upwards transport of solids (e.g., catalyst particles) infast-fluidization or pneumatic conveying fluidization regimes. Fastfluidization and pneumatic conveying fluidization regimes arecharacterized by superficial gas velocities (U) greater than thetransport velocity (U_(tr)). Fast fluidization and pneumatic conveyingfluidization regimes are also described in Kunii, D., Levenspiel, O.,Chapter 3 of Fluidization Engineering, 2^(nd) Edition,Butterworth-Heinemann, Boston, 1991 and Walas, S. M., Chapter 6 ofChemical Process Equipment, Revised 2^(nd) Edition,Butterworth-Heinemann, Boston, 2010. A fluidized bed reactor, such as acirculating fluidized bed reactor, may be operated as a riser reactor.

As used herein, the term “co-current” refers to a flow of two streams(e.g., stream (a), stream (b)) in substantially the same direction. Forexample, if stream (a) flows from a top portion to a bottom portion ofat least one reaction zone and stream (b) flows from a top portion to abottom portion of at least one reaction zone, the flow of stream (a)would be considered co-current to the flow of stream (b). On a smallerscale within the reaction zone, there may be regions where flow may notbe co-current.

As used herein, the term “counter-current” refers to a flow of twostreams (e.g., stream (a), stream (b)) in substantially opposingdirections. For example, if stream (a) flows from a top portion to abottom portion of the at least one reaction zone and stream (b) flowsfrom a bottom portion to a top portion of the at least one reactionzone, the flow of stream (a) would be considered counter-current to theflow of stream (b). On a smaller scale within the reaction zone, theremay be regions where flow may not be counter-current.

Acyclic C5 Conversion Process

The process for the conversion of an acyclic C5 hydrocarbon to a productcomprising cyclic C5 compounds comprises contacting the C5 feedstockand, optionally, hydrogen under acyclic C5 conversion conditions in thepresence of one or more catalyst compositions, including but not limitedto the catalyst compositions described herein, to form said product. Theproduct of the process for conversion of an acyclic C5 feedstockcomprises cyclic C5 compounds. The cyclic C5 compounds can comprise oneor more of cyclopentane, cyclopentene, cyclopentadiene, and includesmixtures thereof.

In one or more embodiments, the acyclic C5 conversion conditions includeat least a temperature, a partial pressure, and a weight hourly spacevelocity (WHSV). The temperature is in the range of about 400° C. toabout 700° C., or in the range from about 450° C. to about 650° C.,preferably, in the range from about 500° C. to about 600° C. The partialpressure is in the range of about 3 to about 100 psi (21 to 689kilopascal), or in the range from about 3 to about 50 psi (21 to 345kilopascal), preferably, in the range from about 3 to about 20 psi (21to 138 kilopascal). The weight hourly space velocity is in the rangefrom about 1 to about 50 hr⁻¹, or in the range from about 1 to about 20hr⁻¹. Such conditions include a molar ratio of the optional hydrogenco-feed to the acyclic C5 hydrocarbon in the range of about 0 to 3, orin the range from about 0.5 to about 2. Such conditions may also includeco-feed C1-C4 hydrocarbons with the acyclic C5 feed.

In one or more embodiments, this invention relates to a process forconversion of n-pentane to cyclopentadiene comprising the steps ofcontacting n-pentane and, optionally, hydrogen (if present, typically H₂is present at a molar ratio of hydrogen to n-pentane of 0.01 to 3.0)with one or more catalyst compositions, including but not limited to thecatalyst compositions described herein, to form cyclopentadiene at atemperature of 400° C. to 700° C., a partial pressure of 3 to about 100psia, and a weight hourly space velocity of 1 to about 50 hr⁻¹.

In the presence of the catalyst, a number of desired and undesirableside reactions may take place. The net effect of the reactions is theproduction of hydrogen and the increase of total volume (assumingconstant total pressure). One particularly desired overall reaction(i.e., intermediate reaction steps are not shown) is:n-pentane→CPD+3H₂.

Additional overall reactions include, but are not limited to:n-pentane→1,3-pentadiene+2H₂,n-pentane→1-pentene+H₂,n-pentane→2-pentene+H₂,n-pentane→2-methyl-2-butene+H₂,n-pentane→cyclopentane+H₂,cyclopentane→cyclopentene+H₂, orcyclopentene→CPD+H₂.

Fluids inside the first reactor are essentially in gas phase. At theoutlet of the first reactor, a first reactor hydrocarbon effluent,preferably in gas phase, is obtained. The first reactor hydrocarboneffluent may comprise a mixture of the following hydrocarbons, amongothers: heavy components comprising more than 8 carbon atoms such asmultiple-ring aromatics; C8, C7, and C6 hydrocarbons such as one-ringaromatics; CPD (the desired product); unreacted C5 feedstock materialsuch as n-pentane; C5 by-products such as pentenes (1-pentene,2-pentene, e.g.), pentadienes (1,3-pentadiene, 1,4-pentadiene, e.g.),cyclopentane, cyclopentene, 2-methylbutane, 2-methyl-1-butene,3-methyl-1-butene, 2-methyl-1,3-butadiene, 2,2-dimethylpropane, and thelike; C4 by-products such as butane, 1-butene, 2-butene, 1,3-butadiene,2-methylpropane, 2-methyl-1-propene, and the like; C3 by-products suchas propane, propene, and the like; C2 by-products such as ethane andethene, methane, and hydrogen.

The first reactor hydrocarbon effluent may comprise CPD at aconcentration of C(CPD)1 wt %, based on the total weight of the C5hydrocarbons in the first reactor hydrocarbon effluent; anda1≦C(CPD)1≦a2, where a1 and a2 can be, independently, 15, 16, 18, 20,22, 24, 25, 26, 28, 30, 32, 34, 35, 36, 38, 40, 45, 50, 55, 60, 65, 70,75, 80, or 85 as long as a1<a2. The first reactor hydrocarbon effluentmay comprise acyclic diolefins at a total concentration of C(ADO)1 wt %,based on the total weight of the C5 hydrocarbons in the first reactorhydrocarbon effluent; and b1≦C(ADO)1≦b2, where b1 and b2 can be,independently, 20, 18, 16, 15, 14, 12, 10, 8, 6, 5, 4, 3, 2, 1, or 0.5,as long as b1<b2. Preferably, 0.5≦C(ADO)≦10. Preferably, the acyclicdiolefins comprise 1,3-pentadiene at a concentration of C(PTD)1 wt %,based on the total weight of C5 components in the first reactorhydrocarbon effluent; and c1≦C(PTD)1≦c2, where c1 and c2 can be,independently, 20, 18, 16, 15, 14, 12, 10, 8, 6, 5, 4, 3, 2, 1, 0.5, or0.3, as long as c1<c2.

As a result of the use of the catalyst and the choice of reactionconditions in the first reactor, a high CPD to acyclic diolefin molarratio in the first reactor hydrocarbon effluent can be achieved suchthat C(CPD)1/C(ADO)1≧1.5, preferably 1.6, 1.8, 2.0, 2.2, 2.4, 2.5, 2.6,2.8, 3.0, 3.2, 3.4, 3.5, 3.6, 3.8, 4.0, 5.0, 6.0, 8.0, 10, 12, 14, 15,16, 18, or 20. The high ratio of C(CPD)1/C(ADO)1 significantly reducesCPD loss as a result of Diels-Alder reactions between CPD and acyclicdienes in subsequent processing steps, and therefore, allows theprocesses of the present invention to achieve high DCPD yield and highDCPD purity for the subsequently produced DCPD fractions.

Desirably, the total absolute pressure and temperature of the firstreactor hydrocarbon effluent should be maintained at levels such thatthe dimerization of CPD to form DCPD is substantially avoided, and theDiels-Alder reactions between CPD and acyclic dienes are substantiallyinhibited.

Catalyst Composition

Catalyst compositions useful herein include microporous crystallinemetallosilicates, such as crystalline aluminosilicates, crystallineferrosilicates, or other metal containing crystalline silicates (such asthose where the metal or metal containing compound is dispersed withinthe crystalline silicate structure and may or may not be a part of thecrystalline framework). Microporous crystalline metallosilicateframework types useful as catalyst compositions herein include, but arenot limited to, MWW, MFI, LTL, MOR, BEA, TON, MTW, MTT, FER, MRE, MFS,MEL, DDR, EUO, and FAU.

Particularly suitable microporous metallosilicates for use hereininclude those of framework type MWW, MFI, LTL, MOR, BEA, TON, MTW, MTT,FER, MRE, MFS, MEL, DDR, EUO, and FAU where one or more metals fromgroups 8, 11, and 13 of the Periodic Table of the Elements (preferablyone or more of Fe, Cu, Ag, Au, B, Al, Ga, and or In) are incorporated inthe crystal structure during synthesis or impregnated postcrystallization. It is recognized that a metallosilicate may have one ormore metals present and, for example, a material may be referred to as aferrosilicate but it will most likely still contain small amounts ofaluminum.

The microporous crystalline metallosilicates preferably have aconstraint index of less than 12, alternately from 1 to 12, alternatelyfrom 3 to 12. Aluminosilicates useful herein have a constraint index ofless than 12, such as 1 to 12, alternately 3 to 12, and include, but arenot limited to Zeolite beta, mordenite, faujasite, Zeolite L, ZSM-5,ZSM-11, ZSM-22, ZSM-23, ZSM-35, ZSM-48, ZSM-50, ZSM-57, ZSM-58, MCM-22family materials and mixtures of two or more thereof. In a preferredembodiment, the microporous crystalline aluminosilicate has a constraintindex of about 3 to about 12 and is ZSM-5.

ZSM-5 is described in U.S. Pat. No. 3,702,886. ZSM-11 is described inU.S. Pat. No. 3,709,979. ZSM-22 is described in U.S. Pat. No. 5,336,478.ZSM-23 is described in U.S. Pat. No. 4,076,842. ZSM-35 is described inU.S. Pat. No. 4,016,245. ZSM-48 is described in U.S. Pat. No. 4,375,573,ZSM-50 is described in U.S. Pat. No. 4,640,829, and ZSM-57 is describedin U.S. Pat. No. 4,873,067. ZSM-58 is described in U.S. Pat. No.4,698,217. Constraint index and a method for its determination aredescribed in U.S. Pat. No. 4,016,218. The entire contents of each of theaforementioned patents are incorporated herein by reference.

The MCM-22 family material is selected from the group consisting ofMCM-22, PSH-3, SSZ-25, MCM-36, MCM-49, MCM-56, ERB-1, EMM-10, EMM-10-P,EMM-12, EMM-13, UZM-8, UZM-8HS, ITQ-1, ITQ-2, ITQ-30, and mixtures oftwo or more thereof.

Materials of the MCM-22 family include MCM-22 (described in U.S. Pat.No. 4,954,325), PSH-3 (described in U.S. Pat. No. 4,439,409), SSZ-25(described in U.S. Pat. No. 4,826,667), ERB-1 (described in EP 0 293032), ITQ-1 (described in U.S. Pat. No. 6,077,498), and ITQ-2 (describedin WO 97/17290), MCM-36 (described in U.S. Pat. No. 5,250,277), MCM-49(described in U.S. Pat. No. 5,236,575), MCM-56 (described in U.S. Pat.No. 5,362,697), and mixtures of two or more thereof. Related zeolites tobe included in the MCM-22 family are UZM-8 (described in U.S. Pat. No.6,756,030) and UZM-8HS (described in U.S. Pat. No. 7,713,513), both ofwhich are also suitable for use as the molecular sieve of the MCM-22family.

In one or more embodiments, the microporous crystalline metallosilicatehas an Si/M molar ratio greater than about 3, or greater than about 25,or greater than about 50, or greater than about 100, or greater than400, or in the range from about 100 to about 2,000, or from about 100 toabout 1,500, or from about 50 to 2,000, or from about 50 to 1,200.

In one or more embodiments, the microporous crystalline aluminosilicatehas an SiO2/Al2O3 molar ratio greater than about 3, or greater thanabout 25, or greater than about 50, or greater than about 100, orgreater than 400, or in the range from about 100 to about 400, for fromabout 100 to about 500, or from about 25 to about 2,000, or from about50 to about 1,500, or from about 100 to 1,200 from about 100 to 1000.

In another embodiment of the invention, the microporous crystallinemetallosilicate (such as an aluminosilicate) is combined with a Group 10metal or metal compound, and, optionally, one, two, three or more Group1, 2, or 11 metals or metal compounds.

In one or more embodiments, the Group 10 metal includes, or is selectedfrom the group consisting of, Ni, Pd, and Pt, preferably Pt. The Group10 metal content of said catalyst composition is at least 0.005 wt %,based on the weight of the catalyst composition. In one or moreembodiments, the Group 10 content is in the range from about 0.005 wt %to about 10 wt %, or from about 0.005 wt % up to about 1.5 wt %, basedon the weight of the catalyst composition.

In one or more embodiments, the Group 1 alkali metal includes, or isselected from the group consisting of, Li, Na, K, Rb, Cs, and mixturesof two or more thereof, preferably Na.

In one or more embodiments, the Group 2 alkaline earth metal is selectedfrom the group consisting of Be, Mg, Ca, Sr, Ba, and mixtures of two ormore thereof.

In one or more embodiments, the Group 1 alkali metal is present as anoxide and the metal is selected from the group consisting of Li, Na, K,Rb, Cs, and mixtures of two or more thereof. In one or more embodiments,the Group 2 alkaline earth metal is present as an oxide and the metal isselected from the group consisting of Be, magnesium, calcium, Sr, Ba,and mixtures of two or more thereof. In one or more embodiments, theGroup 1 alkali metal is present as an oxide and the metal is selectedfrom the group consisting of Li, Na, K, Rb, Cs, and mixtures of two ormore thereof; and the Group 2 alkaline earth metal is present as anoxide and the metal is selected from the group consisting of Be,magnesium, calcium, Sr, Ba, and mixtures of two or more thereof.

In one or more embodiments, the Group 11 metal includes, or is selectedfrom the group consisting of, silver, gold, copper, preferably silver orcopper. The Group 11 metal content of said catalyst composition is atleast 0.005 wt %, based on the weight of the catalyst composition. Inone or more embodiments, the Group 11 content is in the range from about0.005 wt % to about 10 wt %, or from about 0.005 wt % up to about 1.5 wt%, based on the weight of the catalyst composition.

In one or more embodiments, the catalyst composition has an Alpha Value(as measured prior to the addition of the Group 10 metal, preferablyplatinum) of less than 25, alternately less than 15, alternately from 1to 25, alternately from 1.1 to 15.

In one or more embodiments of aluminosilicates the molar ratio of saidGroup 1 alkali metal to Al is at least about 0.5, or from at least about0.5 up to about 3, preferably at least about 1, more preferably at leastabout 2.

In one or more embodiments of aluminosilicates, the molar ratio of saidGroup 2 alkaline earth metal to Al is at least about 0.5, or from atleast about 0.5 up to about 3, preferably at least about 1, morepreferably at least about 2.

In one or more embodiments, the molar ratio of said Group 11 metal toGroup 10 metal is at least about 0.1, or from at least about 0.1 up toabout 10, preferably at least about 0.5, more preferably at leastabout 1. In one or more embodiments, the Group 11 alkaline earth metalis present as an oxide and the metal is selected from the groupconsisting of gold, silver, and copper, and mixtures of two or morethereof.

Preferably, catalyst compositions useful herein are employed atconversion conditions including a temperature in the range of from 400to 800° C., a pressure in the range of from 10 to 1,000 kilopascalabsolute, and a WHSV in the range of 1 to 100 hr⁻¹. In one or moreembodiments, the use of the catalyst compositions of this inventionprovides a conversion of at least about 60%, or at least about 75%, orat least about 80%, or in the range from about 60% to about 80%, of saidacyclic C5 feedstock under acyclic C5 conversion conditions of ann-pentane containing feedstock with equimolar Hz, a temperature in therange of about 550° C. to about 600° C., an n-pentane partial pressurebetween 3 and 10 psia, and an n-pentane weight hourly space velocity of10 to 20 hr⁻¹.

In one or more embodiments, the use of any one of the catalystcompositions of this invention provides a carbon selectivity to cyclicC5 compounds of at least about 30%, or at least about 40%, or at leastabout 50%, or in the range from about 30% to about 80%, under acyclic C5conversion conditions including an n-pentane feedstock with equimolarHz, a temperature in the range of about 550° C. to about 600° C., ann-pentane partial pressure between 3 and 10 psia, and an n-pentaneweight hourly space velocity between 10 and 20 hr⁻¹.

In one or more embodiments, the use of any one of the catalystcompositions of this invention provides a carbon selectivity tocyclopentadiene of at least about 30%, or at least about 40%, or atleast about 50%, or in the range from about 30% to about 80%, underacyclic C5 conversion conditions including an n-pentane feedstock withequimolar Hz, a temperature in the range of about 550° C. to about 600°C., an n-pentane partial pressure between 3 and 10 psia, and ann-pentane weight hourly space velocity between 10 and 20 hr⁻¹.

The catalyst compositions of this invention can be combined with amatrix or binder material to render them attrition resistant and moreresistant to the severity of the conditions to which they will beexposed during use in hydrocarbon conversion applications. The combinedcompositions can contain 1 to 99 wt % of the materials of the inventionbased on the combined weight of the matrix (binder) and material of theinvention. The relative proportions of microcrystalline material andmatrix may vary widely, with the crystal content ranging from about 1 toabout 90 wt % and more usually, particularly when the composite isprepared in the form of beads, extrudates, pills, oil drop formedparticles, spray dried particles, etc., in the range of about 2 to about80 wt % of the composite.

During the use of the catalyst compositions in the processes of thisinvention, coke may be deposited on the catalyst compositions, wherebysuch catalyst compositions lose a portion of its catalytic activity andbecome deactivated. The deactivated catalyst compositions may beregenerated by conventional techniques including high pressure hydrogentreatment and combustion of coke on the catalyst compositions with anoxygen-containing gas.

Useful catalyst compositions comprise a crystalline aluminosilicate orferrosilicate, which is optionally combined with one, two or moreadditional metals or metal compounds. Preferred combinations include:

1) a crystalline aluminosilicate (such as ZSM-5 or Zeolite L) combinedwith a Group 10 metal (such as Pt), a Group 1 alkali metal (such assodium or potassium) and/or a Group 2 alkaline earth metal;

2) a crystalline aluminosilicate (such as ZSM-5 or Zeolite L) combinedwith a Group 10 metal (such as Pt) and a Group 1 alkali metal (such assodium or potassium);

3) a crystalline aluminosilicate (such as a ferrosilicate or an irontreated ZSM-5) combined with a Group 10 metal (such as Pt), a Group 1alkali metal (such as sodium or potassium); 4) a crystallinealuminosilicate (Zeolite L) combined with a Group 10 metal (such as Pt)and a Group 1 alkali metal (such as potassium); and5) a crystalline aluminosilicate (such as ZSM-5) combined with a Group10 metal (such as Pt), a Group 1 alkali metal (such as sodium), and aGroup 11 metal (such as silver or copper).

Another useful catalyst composition is a group 10 metal (such as Ni, Pd,and Pt, preferably Pt) supported on silica (e.g., silicon dioxide)modified by a Group 1 alkali metal silicate (such as Li, Na, K, Rb,and/or Cs silicates) and/or a Group 2 alkaline earth metal silicate(such as Mg, Ca, Sr, and/or Ba silicates), preferably potassiumsilicate, sodium silicate, calcium silicate and/or magnesium silicate,preferably potassium silicate and/or sodium silicate. The Group 10 metalcontent of the catalyst composition is at least 0.005 wt %, based on theweight of the catalyst composition, preferably, in the range from about0.005 wt % to about 10 wt %, or from about 0.005 wt % up to about 1.5 wt%, based on the weight of the catalyst composition. The silica (SiO2)may be any silica typically used as catalyst support such as thosemarketed under the trade names of DAVISIL 646 (Sigma Aldrich), DAVISON952, DAVISON 948 or DAVISON 955 (Davison Chemical Division of W.R. Graceand Company).

For more information on useful catalyst compositions, please see filedapplications:

-   1) U.S. Ser. No. 62/250,675, filed Nov. 4, 2015;-   2) U.S. Ser. No. 62/250,681, filed Nov. 4, 2015;-   3) U.S. Ser. No. 62/250,688, filed Nov. 4, 2015;-   4) U.S. Ser. No. 62/250,695, filed Nov. 4, 2015; and-   5) U.S. Ser. No. 62/250,689, filed Nov. 4, 2015;    which are incorporated herein by reference.    Cooling of the First Reactor Hydrocarbon Effluent

To prevent undesirable side reactions such as thermal cracking,condensation of PNAs, and premature Diels-Alder reactions of reactivediolefinic species, especially CPD, it is highly desired that the firstreactor hydrocarbon effluent is cooled down once it exits the firstreactor. To that end, the first reactor hydrocarbon effluent may bepassed through at least one heat exchanger located next to the outletfrom the first reactor where its temperature is lowered to a range fromTc1° C. to Tc2° C., where Tc1 and Tc2 can be, independently, 20, 50, 80,150, 200, 250, 300, 350, 400, or 450° C., as long as Tc1<Tc2.Alternately or additionally, the first reactor hydrocarbon effluent maybe contacted with a quench liquid so that the temperature is lowered toa range from Tc1° C. to Tc2° C., where Tc1 and Tc2 can be,independently, 20, 40, 50, 60, 80, 100, 120, 140, 150, 160, 180, 200,220, 240, 250, 260, 280, 300, 320, 340, 350, 360, 380, 400, 420, 440, or450, as long as Tc1<Tc2. Upon cooling, a majority of the components fromthe first reactor hydrocarbon effluent are still in gas or vapor phase.

Washing/Quenching of the First Reactor Hydrocarbon Effluent

The first reactor hydrocarbon effluent comprises non-negligible amountsof heavy components, including but not limited to: polynuclear aromaticspecies (naphthalene and alkylated naphthalenes, anthracene andalkylated anthracenes, phenanthrene and alkylated phenanthrenes), DCPD,products formed as a result of undesired Diels-Alder reactions betweenCPD and acyclic diolefins. It is highly desired that these heavycomponents, especially C8+ hydrocarbons, are at least partly removedfrom the first reactor hydrocarbon effluent such that contamination ofthe C5-rich fraction and subsequent contamination of DCPD-rich fractionsby them are avoided. For example, naphthalene is very difficult to beremoved from DCPD by distillation; also naphthalene and heavier PNAs cancondense to form solids which can foul equipment. Therefore, naphthaleneand heavier PNAs are desirably removed from the first reactorhydrocarbon effluent before it is further processed.

Advantageously, such heavy components can be effectively removed in avessel by contacting the stream of the first reactor hydrocarboneffluent, preferably after it is being partially cooled down, with awash oil. To that end, the wash oil, desirably in liquid phase duringoperation, can be sprayed into the washing vessel as liquid dropletswhen contacting the substantially vapor stream of the first reactorhydrocarbon effluent. Additionally or alternatively, the substantiallyvapor stream of the first reactor hydrocarbon effluent can be sent to asuitable gas-liquid contacting washing vessel capable of handlingfouling services (e.g., a tower with grids and/or random packing).Sufficient contact between the first reactor hydrocarbon effluent andthe liquid wash oil results in the extraction of the heavy components(i.e., C8+ hydrocarbons) from the substantially vapor stream of thefirst reactor hydrocarbon effluent into the wash oil liquid. A smallamount of the wash oil may be entrained in the first reactor hydrocarboneffluent vapor stream at a low vapor pressure. The entrained wash oilcan be removed subsequently where necessary.

In the washing vessel, the first reactor hydrocarbon effluent vaporstream can be quenched down further to a temperature in a range from 10to 300° C., preferably from 20 to 100° C. Thus, from the washing vessel,a vapor stream of the first reactor hydrocarbon effluent, washed andcooled, is obtained. In addition, a wash oil liquid stream (also called“heavy stream”), comprising multiple-ring aromatics mentioned above, mayalso be obtained.

Various wash oils can be used. Non-limiting examples of the wash oilinclude: cyclohexane; monoalkyl, dialkyl, and trialkyl cyclohexanes;benzene; monoalkyl, dialkyl, and trialkyl benzenes; monoalkyl, dialkyl,trialkyl, and tetraalkyl naphthalenes; other alkylated multiple-ringaromatics; and mixtures and combinations thereof. Preferred wash oilsare: alkyl benzenes and mixtures thereof (herein referred to as lightwash oil); and alkyl naphthalenes and mixtures thereof (herein referredto as heavy wash oil). More preferably, toluene, especially relativelypure toluene with a purity of at least 50 wt %, or alkylnaphthalene(s),especially those with purity of at least 50 wt %, is used as the washoil.

Wash Oil Recovery and/or Recycle

The wash oil used in the present invention is recovered andadvantageously recycled. To that end, the heavy stream exiting at thelower portion of the washing vessel is supplied to a wash oil recoverysub-system, from which (i) a heavy oil fraction comprising themultiple-ring component, typically as a lower stream; (ii) a secondrecovered wash oil stream depleted in multiple-ring components; and(iii) an optional recovered C5-rich stream comprising CPD (describedbelow in greater detail) are obtained. Additionally, a flux oil maypreferentially be supplied to the wash oil recovery sub-system and/orblended with the heavy stream upstream of the wash oil recoverysub-system (e.g., near the tower bottom of the washing vessel). Thisflux oil is chosen to be compatible with the heavy stream and the heavyoil fraction; i.e., precipitation of insoluble species is not allowed tooccur at any of the wash oil recovery sub-system process conditions orat any downstream transportation or storage conditions. The oil fluxdesirably has sufficient solvency and proper solvent volatility.Preferably the flux oil is added at a quantity such that the resultedviscosity of the mixture of the flux oil and the heavy oil fraction at50° C. is less than 600 centistokes (cSt, mm²/second), preferably lessthan 550 cSt, or less than 530 cSt, such as in the range from 150 to 550cSt, or from 180 to 530 cSt, or from 180 to 450 cSt, or from 200 to 400cSt. Candidate sources of flux oil are virgin distillate streams and/orcracked distillate streams including those produced in catalyticcrackers or steam crackers.

As described below, from the first separation sub-system used forseparating the washed first reactor hydrocarbon effluent, and/or otherdownstream equipment and processes, one or more heavy streams comprisingwash oil and/or heavy components depleted in light components may beproduced. Such heavy streams, if any, may be fed into the wash oilrecovery sub-system as well along with the heavy stream rich in wash oilfrom the washing vessel to recover the wash oil and other usefulcomponents therein.

In the fluid channel from the first reactor to the washing vessel,including the heat exchanger in between, if any, and inside the washingvessel, dimerization between CPD molecules may occur to form DCPD, andCPD may react with acyclic diolefins to form other C10+ hydrocarbons. Amajor portion of these heavy components, if formed, are partitioned inthe wash oil liquid stream (the heavy stream) exiting the washingvessel. If the wash oil liquid stream is sent to a fuel disposition orother low value disposition directly, a portion of the CPD produced inthe first reactor would be downgraded to low value. To reduce suchundesirable yield loss, one can operate the wash oil recovery sub-systemunder conditions favoring retro-Diels-Alder reaction (also convenientlyreferred to as reverse dimerization) to convert DCPD and other C10+components to CPD and other C5 species, thereby obtaining an upperrecovered C5-rich stream and a lower wash oil-rich stream containingresidual C8+ and the wash oil. The upper C5-rich stream may be feddirectly or indirectly to a second reactor as part of the first C5-richfraction. The lower wash oil-rich stream can be further distilled torecover at least a portion of the wash oil, which can be recycled to thewash vessel directly or indirectly. Such conditions favoring reversedimerization (retro-Diels-Alder reaction) include, e.g., a temperaturein the range from 150 to 350° C., preferably, from 170 to 260° C., apressure in a range from 21 to 345 kilopascal absolute, preferably from21 to 138 kilopascal absolute, and a residence time from 0.01 to 10hours, preferably from 0.1 to 4 hours.

In one example, the wash oil recovery sub-system comprises twodistillation columns connected in series. The heavy stream from thewashing vessel, the optional heavy stream(s) from the first separationsub-system and other down-stream equipment, and, optionally, a flux oilare fed into the first distillation column, from which a lower streamcomprising the wash oil and rich in the multiple-ring aromatics isobtained and fed into the second distillation column. The firstdistillation column is advantageously operated under conditions favoringreverse dimerization described above. An upper recovered C5-rich streamis obtained from the first distillation column, which can be feddirectly to the second reactor (the first dimerization reactor,described in greater detail below). The first distillation column in thewash oil recovery sub-system can be optionally combined with the washingvessel. In a second distillation column which receives the lower streamfrom the distillation column, an upper, second recovered wash oil streamand a heavy oil fraction stream including multi-ring aromatics and theflux oil, if present, are obtained. The heavy oil fraction stream can beused as fuel or otherwise disposed of A portion of the second recoveredwash oil stream can be directly or indirectly recycled to the washingvessel. Additionally or alternatively, the second recovered wash oilstream can be used to wash a downstream vapor stream rich in lightcomponents to recover low concentrations of C5 hydrocarbons containedtherein in another vessel (called “debutanizer” sometimes, described ingreater detail below), and then recycled to the washing vessel. Often,to prevent buildup of molecules with boiling points close to that of theheavy wash oil, a side stream or purge is withdrawn from the seconddistillation column in the wash oil recovery sub-system.

In another example, the wash oil recovery sub-system comprises adivided-wall distillation column. The heavy stream(s) from the washingvessel; the optional heavy stream(s) from the first separationsub-system and other down-stream equipment; and, optionally, a flux oilare fed into the receiving side of the divided-wall distillation columnas feed streams. From this single distillation column, a lower effluentrich in the heavy fraction (including multiple-ring aromatics and theflux oil, if present), an upper recovered C5-rich stream, and a middleeffluent rich in the wash oil as the second recovered wash oil stream onside of the dividing wall opposite to the feed stream(s), can beproduced simultaneously from a single column. The heavy fraction lowerstream can be used as fuel or otherwise disposed of. A portion of thesecond recovered wash oil stream can be directly or indirectly recycledto the washing vessel as described above in connection with thetwo-column example. Because the majority of the feed stream(s) can bethe wash oil, use of a divided-wall distillation column can beparticularly advantageous in cost and energy efficiency.

Separation of the First Reactor Hydrocarbon Effluent

The first reactor hydrocarbon effluent, which is preferably cooled atthe outlet of the first reactor as described above, and washed in awashing vessel as described above is then processed in a firstseparation sub-system to obtain a C5-rich fraction that is depleted ofC1-C4 hydrocarbons and hydrogen, and desirably, depleted of heavycomponents such as C8+ hydrocarbons. Due to the nature of the reactionstaking place in the first reactor, substantial volume of hydrogen ispresent in the first reactor hydrocarbon effluent. Effective separationof hydrogen and C1-C4 light hydrocarbons from the C5 hydrocarbons(including CPD) needs to take into consideration that much of the C5hydrocarbons can be held as vapor in the hydrogen/light hydrocarbonstream. Thus, desirably, a compression train with inter-stage coolingand liquid/vapor separation can be advantageously used as the firstseparation sub-system to minimize the loss of C5 hydrocarbons to thehydrogen and light hydrocarbon stream.

Exemplary compression trains with inter-stage cooling and liquid/vaporseparation are those comprising at least 3-stages ofcompression/inter-stage cooling with an exiting pressure from the laststage of at least 100 psia (689 kilopascal absolute).

From the first separation sub-system (a compression train, e.g.), one ormore streams of C5-rich hydrocarbon (the first C5-rich fraction) may beobtained from the multiple stages. Where multiple streams of the firstC5-rich fractions are obtained, two or more of them may be optionallycombined into a single first C5-rich rich fraction stream and thenprocessed together subsequently. The first C5-rich fraction generallycomprises: (i) CPD; (ii) unreacted C5 hydrocarbon(s) from the C5feedstock such as n-pentane; and (iii) cyclopentane and cyclopentene.

The first C5-rich fraction may further comprise a portion of the washoil, especially if the wash oil contains C6 and C7 hydrocarbons, such ascyclohexane and alkylcyclohexanes, benzene and alkylbenzenes (e.g.,toluene). Such wash oil may be removed subsequently where necessary.Even if high boiling point wash oils such as alkyl naphthalenes areused, the first C5-rich fraction may comprise C6 hydrocarbons (asby-products from the first reactor) such as benzene at a lowconcentration.

From the first separation sub-system (the first liquid/vapor separatorin a multi-stage compression train, e.g.), an optional heavy-containingstream may be produced, especially at one of the early stages,comprising wash oil and C8+ hydrocarbons (DCPD, and other products as aresult of the Diels-Alder reactions between CPD and other dienes, e.g.),and the like. Such heavy stream can be in non-negligible quantity ifhigh boiling point wash oil such as methylnaphthalene(s) is used. Ifsuch heavy stream is produced from the compression train, it may beadvantageously combined with the wash oil liquid stream produced fromthe washing vessel described above, and then processed togethersubsequently as described above.

From the first separation sub-system (a compression train, e.g.), alight components-rich fraction comprising hydrogen and C1-C4hydrocarbons is also obtained. This light components-rich fraction isdesirably depleted of C5 components, especially CPD, or at leastminimized, such that C5 molecules are used to the highest degree in theprocess of the present invention. If the light components-rich fractionexiting the first separation sub-system contains C5 components at anon-negligible amount, one may wash it in a washing vessel (an absorber)where it is contacted with a solvent (e.g., the wash oil used in thewashing vessel described above), such as a fresh solvent stream orand/or at least a portion of the second recovered wash oil stream fromthe wash-oil recovery sub-system described above, such that the C5components are substantially extracted by the solvent (e.g., the washoil). The bottom stream from said absorber can then be delivered to thewashing vessel for washing the first reactor hydrocarbon effluent asdescribed above. The thus washed light components-rich fraction is thensubstantially depleted in C5 hydrocarbons.

Separation of the Light Components-Rich Fraction and Recycling ofHydrogen and/or Light Hydrocarbons

A significant component of the light components-rich fraction comingfrom the first separation sub-system separating the first reactorhydrocarbon effluent is hydrogen gas. C1-C4 hydrocarbons are produced atsmall quantities in the first reactor from the C5 feedstock.Alternatively, in certain exemplary processes of the present invention,a C1-C4 light hydrocarbon, such as CH₄, may be supplied to the firstreactor as a co-feedstock, resulting in higher concentrations of theC1-C4 light hydrocarbons in the light components-rich fraction obtainedfrom the first separation sub-system.

Given the large quantity of hydrogen produced in the process, it isdesirable to separate the light components-rich fraction to obtain ahigher purity hydrogen stream, which can be used or sold as a highlyvaluable industrial gas. To that end, various processes and equipmentmay be used to recover and concentrate hydrogen, such as pressure-swingadsorption (PSA), rapid cycle pressure-swing adsorption (RCPSA),thermal-swing adsorption (TSA), cryogenic processes, membraneseparation, and the like, with PSA or RCPSA being preferred. By usingany of these processes or any combinations thereof, it is possible toobtain three gas streams from the light components-rich fraction: ahydrogen-rich stream comprising hydrogen at a purity of at least 95 mol%, based on the total moles of the hydrogen-rich stream; a middle streamcomprising hydrogen and C1-C4 hydrocarbons that is preferably low in C2+hydrocarbons; and a C1-C4-rich hydrocarbon stream which may also containC5+ hydrocarbons which can be subsequently recovered by washing or lowtemperature fractionation (absorber, e.g.). A portion of thehydrogen-rich stream and/or a portion of the middle stream (if C1-C4hydrocarbon is co-fed into the first reactor) can be recycled to thefirst reactor. Additionally or alternatively, at least a portion of themiddle stream and/or the C1-C4 hydrocarbon stream can be used as fuelgas to produce the thermal energy needed for certain steps (such as theconversion process in the first reactor) in the process of the presentinvention. Alternatively, the C1-C4-rich hydrocarbon stream can beutilized as a feedstock for other process such as light olefinsproduction and/or further processed to obtain an LPG fraction.

As discussed above, the recycle hydrogen may be advantageously admixedwith at least a portion of the C5 feedstock before being fed into thefirst reactor to reduce coke formation on the catalyst particles,thereby increasing the life of the catalyst used in the first reactor.Additionally or alternatively, the recycle hydrogen may be fedseparately into the first reactor. Additionally or alternatively, therecycle hydrogen may be utilized for rejuvenation or reduction of thecatalyst.

Dimerization of the First C5-Rich Fraction

The first C5-rich fraction advantageously comprises CPD at a highconcentration in a range from ca1 wt % to ca2 wt %, based on the totalweight of C5 hydrocarbons in the first C5-rich fraction, where ca1 andca2 can be, independently, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70,75, 80, 85, or 90, as long as ca1<ca2. Such CPD may be used directly asa CPD feed for the production of, e.g., norbornene, vinyl norbornene,ethylidene norbornene, hydrocarbon resin adhesives or tackifiers,unsaturated polyester resins, cyclopentane, and/or cyclopentene.

Additionally or alternatively, at least a portion of the first C5-richfraction can be supplied to a first dimerization reactor (the secondreactor in the system) operating under a first set of dimerizationconditions, where a portion of the CPD is advantageously converted intoDCPD. This can be highly desirable because DCPD is much more stable thanCPD, and therefore can be stored and/or transported to a differentlocation where it is used as DCPD or converted into CPD and used for theproduction of value-added products.

The first dimerization reactor (the second reactor in the system) can beadvantageously a plug flow reactor, a back mixed reactor, a continuousstirred-tank reactor, a boiling point reactor, and/or a baffled reactor;additionally the reactor may contain heat transfer devices such ascoils. The first dimerization reactor may consist of one or morereaction zones within a single vessel or in multiple vessels and mayinclude one or more heat exchanging devices within the reaction zones orbetween the reaction zones.

The first set of dimerization conditions in the first dimerizationreactor can advantageously include: a temperature in the range from Tb1°C. to Tb2° C., where Tb1 and Tb2 can be, independently, 30, 50, 60, 80,100, 120, 140, 150, 160, 180, 200, 220, 240, or 250, as long as Tb1<Tb2;an absolute pressure in the range from Pb1 kilopascal to Pb2 kilopascal,where Pb1 and Pb2 can be, independently, 345, 350, 400, 450, 500, 550,600, 700, 800, 900, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500,5000, 6000, 6500, 6894, or 7000, as long as Pb1<Pb2; and a residencetime in the range from Tr1 minutes to Tr2 minutes, where Tr1 and Tr2 canbe, independently, 1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120,130, 140, 150, 160, 170, 180, 190, 200, 210, or 220, as long as Tr1<Tr2.Preferably, if two dimerization reactors in series are utilized in thesystem, the first set of dimerization conditions include a temperaturein the range from 70 to 130° C., a total pressure in the range from 689to 3447 kilopascal absolute, and a residence time in the range from 20to 200 minutes, such as from 100 to 200 minutes; preferably, if threedimerization reactors in series are utilized in the system, the firstset of dimerization conditions include a temperature in the range from90 to 140° C., a total pressure in the range from 689 to 3447 kilopascalabsolute, and a residence time in the range from 1 to 30 minutes.

A portion of the CPD contained in the first C5-rich fraction suppliedinto the first dimerization reactor is converted into DCPD. At theoutlet of the second reactor (the first dimerization reactor), a secondreactor effluent is obtained comprising CPD and DCPD. Preferably, thedegree of conversion in the second reactor is limited so that highpurity DCPD may be produced; i.e., the extent of conversion is limitedso that the quantity of CPD co-dimers with acyclic dienes and monoolefins is maintained below a level so as to be able to obtain thedesired purity of DCPD.

Separation of the First DCPD-Rich Fraction

At least a portion of the second reactor effluent is then supplied to asecond separation device, such as a distillation column, where a firstDCPD-rich fraction (as a lower stream such as a bottom effluent from thecolumn, e.g.) and a second C5-rich fraction (as an upper stream such asan overhead effluent from the column, e.g.) are obtained.Advantageously, the first DCPD-rich fraction can have a DCPDconcentration of C(DCPD)1 wt %; and x1≦C(DCPD)1≦x2, wherein x1 and x2can be, independently, 80, 82, 84, 85, 86, 88, 90, 91, 92, 93, 94, 95,96, 97, 98, 99, 99.2, 99.4, 99.5, 99.6, 99.8, or 100, as long as x1<x2.Ultra high purity DCPD (i.e., UHP DCPD) with a concentration of at least98 wt %, 99 wt %, or even 99.5 wt %, can be obtained as the firstDCPD-rich fraction. At least a portion of the first DCPD-rich fractioncan be optionally supplied to at least another separation device, suchas a distillation column, where the purity of the first DCPD-richfraction can be further increased. CPD concentration in the secondC5-rich fraction tends to be lower than in the first C5-rich fraction.

Dimerization of the Second C5-Rich Fraction

At least a portion of the second C5-rich fraction obtained from thesecond separation device may advantageously comprise CPD at a highconcentration in the range from ca3 wt % to ca4 wt %, based on the totalweight of C5 hydrocarbons in the second C5-rich fraction, where ca3 andca4 can be, independently, 1, 5, 10, 20, 25, 30, 35, 40, 45, 50, 55, or60, as long as ca3<ca4. Such CPD in the second C5-rich fraction may bedirectly used as a CPD feed for the production of, e.g., norbornene,vinyl norbornene, ethylidene norbornene, hydrocarbon resin adhesives ortackifiers, unsaturated polyester resins, cyclopentane, and/orcyclopentene.

Additionally or alternatively, the second C5-rich fraction can besupplied to a second dimerization reactor (the third reactor in thesystem) operating under a second set of dimerization conditions, where aportion of the CPD is advantageously converted into DCPD, similar to theoperation in the first dimerization reactor (the second reactor in thesystem) but preferably operating at a higher temperature and/or longerresidence time to enable satisfactory conversion of the lowerconcentration CPD.

Thus, the second set of dimerization conditions in the seconddimerization reactor can advantageously include: a temperature in therange from Tb3° C. to Tb4° C., where Tb3 and Tb4 can be, independently,30, 50, 60, 80, 100, 120, 140, 150, 160, 180, 200, 220, 240, or 250, aslong as Tb3<Tb4; an absolute pressure in the range from Pb3 kilopascalto Pb4 kilopascal, where Pb3 and Pb4 can be, independently, 345, 350,400, 450, 500, 550, 600, 700, 800, 900, 1000, 1500, 2000, 2500, 3000,3500, 4000, 4500, 5000, 6000, 6500, 6894, or 7000, as long as Pb3<Pb4;and a residence time in the range from Tr3 minutes to Tr4 minutes, whereTr3 and Tr4 can be, independently, 1, 10, 20, 30, 40, 50, 60, 70, 80,90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220,230, 240, 250, 260, 270, 280, 290, or 300 as long as Tr3<Tr4.Preferably, if two dimerization reactors in series are utilized in thesystem, the second set of dimerization conditions include a temperaturein the range from 75 to 140° C., such as from 100 to 140° C., a totalpressure in the range from 689 to 3447 kilopascal absolute, and aresidence time in the range from 100 to 300 minutes, such as from 150 to300 minutes; preferably, if three dimerization reactors in series areutilized in the system, the second set of dimerization conditionsinclude a temperature in the range from 100 to 140° C., a total pressurein the range from 689 to 3447 kilopascal absolute, and a residence timein the range from 1 to 30 minutes.

The second dimerization reactor (the third reactor in the system) can bea reactor similar to the first dimerization reactor (the second reactorin the system).

A portion of the CPD contained in the second C5-rich fraction suppliedinto the second dimerization reactor is converted into DCPD. At theoutlet of the second dimerization reactor), a third reactor effluent isobtained comprising CPD and DCPD. Preferably, the degree of conversionin the third reactor is limited so that high purity DCPD may beproduced; i.e., the extent of conversion is limited so that the quantityof CPD co-dimers with acyclic dienes and mono olefins is maintainedbelow a level so as to be able to obtain the desired purity of DCPD.

Separation of a Second DCPD-Rich Fraction

At least a portion of the third reactor effluent can be then supplied toa third separation device, such as a distillation column, where a secondDCPD-rich fraction (as a lower stream such as a bottom effluent from thecolumn, e.g.) and a third C5-rich fraction (as an upper stream such asan overhead effluent from the column, e.g.) are obtained.Advantageously, the second DCPD-rich fraction can have a DCPDconcentration of C(DCPD)2 wt %; and x3≦C(DCPD)2≦x4, wherein x3 and x4can be, independently, 40, 50, 60, 65, 70, 75, 80, 82, 84, 85, 86, 88,90, 91, 92, 93, 94, 95, 96, 97, 98, or 99 as long as x3<x4. Usually, thepurity of the second DCPD-rich fraction is lower than the firstDCPD-rich fraction because of the lower ratio of CPD to acyclicdiolefins in the second C5-rich fraction than the first C5-richfraction. Nonetheless, very high purity DCPD (HP DCPD) with aconcentration of at least 90 wt %, or 92 wt %, or 93 wt %, or even 95 wt% can be obtained as the second DCPD-rich fraction. At least a portionof the second DCPD-rich fraction can be optionally supplied to at leastanother separation device, such as a distillation column, where thepurity of the second DCPD-rich fraction can be further increased.Likewise, CPD concentration in the third C5-rich fraction tends to belower than in the second C5-rich fraction.

Dimerization of the Third C5-Rich Fraction

At least a portion of the third C5-rich fraction obtained from the thirdseparation device may advantageously comprise CPD at a concentration inthe range from ca5 wt % to ca6 wt %, based on the total weight of the C5hydrocarbons in the third C5-rich fraction, where ca5 and ca6 can be,independently, 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, or 60, aslong as ca5<ca6. Such CPD in the third C5-rich fraction may be directlyused as a CPD feed for the production of, e.g., norbornene, vinylnorbornene, ethylidene norbornene, hydrocarbon resin adhesives ortackifiers, unsaturated polyester resins, cyclopentane, and/orcyclopentene.

Additionally or alternatively, at least a portion of the third C5-richfraction can be supplied to a third dimerization reactor (the fourthreactor in the system) operating under a third set of dimerizationconditions, where a portion of the CPD is advantageously converted intoDCPD, similar to the operation in the first dimerization reactor (thesecond reactor in the system).

The third dimerization reactor (the fourth reactor in the system) can bea reactor similar to the first dimerization reactor (the second reactorin the system), but preferably operating at a higher temperature and/orlonger residence time to enable satisfactory conversion of the lowerconcentration CPD.

Desirably, a majority of the CPD contained in the third C5-rich fractionsupplied into the third dimerization reactor is converted into DCPD.Additionally or alternatively, it is desirable to react acyclic C5diolefins (e.g., 1,3-pentadiene; 1,4-pentadiene, 1,2-pentadiene, and/or2-methyl-1,3-butadiene) with CPD to produce co-dimers in the thirddimerization reactor. Additionally or alternatively, additional streamscontaining acyclic C5 diolefins (e.g., steam cracked naphtha, light catnaphtha, heavy cat naphtha) and/or C6 diolefins (e.g., methylcyclopentadiene and hexadienes) may be added to the feed to the thirddimerization reactor. Additionally, trimers and tetramers of the C5 andC6 species may also be advantageously produced. At the outlet of thethird dimerization reactor, a fourth reactor effluent is obtainedcomprising CPD and DCPD, preferably in combination with other C5co-dimers, -trimers, and/or -tetramers.

Thus, the third set of dimerization conditions in the third dimerizationreactor can advantageously include: a temperature in the range from Tb5°C. to Tb6° C., where Tb5 and Tb6 can be, independently, 30, 50, 60, 80,100, 120, 140, 150, 160, 180, 200, 220, 240, or 250, as long as Tb5<Tb6;an absolute pressure in the range from Pb5 kilopascal to Pb6 kilopascal,where Pb5 and Pb6 can be, independently, 345, 350, 400, 450, 500, 550,600, 700, 800, 900, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500,5000, 6000, 6500, 6894, or 7000, as long as Pb5<Pb6; and a residencetime in the range from Tr5 minutes to Tr6 minutes, where Tr5 and Tr6 canbe, independently, 100, 200, 300, 400, 500, 600, 700, 800, 900, or 1000,as long as Tr5<Tr6. Preferably, the third set of dimerization conditionsinclude a temperature in the range from 80 to 150° C., such as from 100to 150° C., a total pressure in the range from 689 to 3447 kilopascalabsolute, and a residence time in the range from 150 to 300 minutes.

Separation of a Third DCPD-Rich Fraction

At least a portion of the fourth reactor effluent can then be suppliedto a fourth separation device, such as a distillation column, where athird DCPD-rich fraction (as a bottom effluent from the column, e.g.)and fourth C5-rich fraction (as an overhead effluent from the column,e.g.) are obtained. Advantageously, the third DCPD-rich fraction canhave a DCPD concentration of C(DCPD)3 wt %; and x5≦C(DCPD)3≦x6, whereinx5 and x6 can be, independently, 20, 30, 40, 45, 50, 55, 60, 65, 70, 75,80, 82, 84, 85, 86, 88, 90, 91, 92, 93, 94, or 95, as long as x5<x6.Usually, the purity of the third DCPD-rich fraction is lower than thesecond DCPD-rich fraction because of the lower ratio of CPD to acyclicdienes in the third C5-rich fraction than the second C5-rich fraction.Nonetheless, moderate purity DCPD with a concentration of at least 70 wt%, 75 wt %, 80 wt %, 85 wt %, or 90 wt % can be obtained as the thirdDCPD-rich fraction. At least a portion of the third DCPD-rich fractioncan be optionally supplied to at least another separation device, suchas a distillation column, where the purity of the third DCPD-richfraction can be further increased. Likewise, CPD concentration in thefourth C5-rich fraction tends to be lower than in the third C5-richfraction.

Recycling of C5-Rich Fractions to the First Reactor

At least a portion of the first, second, third, and fourth C5-richfractions described above, if produced at all in the process of thepresent invention, can be recycled to the first reactor described above,where the unreacted C5 hydrocarbon(s) and partially converted C5hydrocarbons from the C5 feedstock can be further converted into CPD.

The first, second, third, and fourth C5-rich fractions, if produced, maycontain C6+ hydrocarbons, such as cyclohexane, benzene, toluene, and thelike. To prevent the accumulation of such C6+ components in the reactionproduct in the first reactor, it is highly desirable that, prior tobeing recycled to the first reactor, at least a portion of the C6+components is separated and removed from the C5-rich stream in aseparation device, such as a distillation column, to produce a fifthC5-rich stream and a C6+-rich stream. Thus, a purified fifth C5-richfraction is then recycled to the first reactor.

Forming Mogas Blending Components from the C5+ Components

Mogas is a blended mixture comprising C4 through C12 hydrocarbons havingan initial normal boiling point of about 35° C. and a final boilingpoint of about 200° C. Mogas is used primarily as fuel for internalcombustion engines in automotive vehicles. There are many differentmogas specifications that have been mandated by various local, state ornational governmental agencies. One example is Reid Vapor Pressure (RVP)of final mogas product. The vapor pressure of mogas is a measure of itsvolatility and high vapor pressures resulting in high evaporativeemissions of smog-forming hydrocarbons.

From a performance standpoint, an important attribute of mogas is itsoctane rating. Linear paraffinic hydrocarbons (i.e., straight-chainsaturated molecules) tend to have lower octane ratings than otherhydrocarbons such as aromatics, olefins, and branched paraffins. To thatend, many of the refining processes used in petroleum refineries aredesigned to produce hydrocarbons with these latter molecularconfigurations. For example, catalytic reforming is a widely practicedindustrial process used to convert naphtha feed typically havinglow-octane ratings into high-octane liquid products to make premiumblending stocks for mogas. The process converts paraffins and naphthenesinto high-octane aromatic hydrocarbons. However, naphtha catalyticreforming is limited to C6+ feedstocks.

Converting n-pentane to isopentane (a/k/a i-pentane) can result in afavorable increase in octane but also an unfavorable increase in theRVP. Conversion of n-pentane to cyclopentyl and internal olefinicspecies—which occurs in the first reactor in the presentinvention—favorably increases the octane and favorably decreases theRVP. DCPD-rich streams may also be partially or fully hydrogenated toproduce a low RVP/higher octane blend component.

Thus, additionally or alternatively, at least a portion of the first,second, third, fourth, and fifth C5-rich fractions and the C6+-richstream described above, if produced at all in the process of the presentinvention, can be optionally combined with additional streams containingdiolefins (e.g., steam cracked naphtha, light cat naphtha, heavy catnaphtha) and can be selectively hydrogenated to produce a mogascomponent. Because the first, second, third, fourth, and fifth C5-richfractions contain high concentrations of unsaturated C5 hydrocarbons,including CPD and cyclopentene, once partially hydrogenated they tend tohave higher octane-value and lower Reid Vapor Pressure (RVP) than theacyclic saturated C5 feedstock supplied to the first reactor. As usedherein, a “selective hydrogenation” process is a treatment of a mixturecomprising both diolefins and mono olefins with hydrogen in the presenceof a selective hydrogenation catalyst under selective hydrogenationconditions favoring the conversion of diolefins into mono olefins overthe conversion of mono olefins into saturates. It is highly desired thatthe selectively hydrogenated mogas component comprises diolefins at atotal concentration not higher than 1.0 wt %, based on the total weightof the mogas component. Thus, mogas component can then be blended withadditional mogas components to obtain mogas with the desired compositionand properties.

Additionally or alternatively, prior to or after hydrogenation thereof,at least a portion of the first, second, third, fourth, and fifthC5-rich fractions described above, if produced at all in the process ofthe present invention, and/or a portion of their hydrogenated products,may be separated to obtain high-purity cyclopentene, cyclopentane,2-methyl-1,3-butadiene, and/or 1,3-pentadiene, each of which can be usedor sold as valuable industrial materials.

Non-limiting examples of hydrogenation catalyst include: palladium-basedor nickel-based catalysts. Exemplary hydrogenation conditions include: atemperature in the range from 30-250° C. and a pressure in the rangefrom 1,700-5,500 kilopascal absolute.

The present invention can be used to convert low value C5 feedstock intohigher value CPD, DCPD, mogas components with high octane and/or lowerRVP, cyclopentene, cyclopentane, 1,3-pentadiene, and the like, andhydrogen.

DESCRIPTION ACCORDING TO THE DRAWINGS

The drawings schematically illustrate the block flow diagrams ofexemplary system(s) and sub-system(s) thereof of the present inventionoperating to implement exemplary process(es) or aspects thereof of thepresent invention. It should be understood that only major componentsare shown in the drawings. Auxiliary equipment such as control valves,pumps, heat exchangers, reboilers, recycle loop, and the like, althoughnot all shown in all drawings, are used liberally throughout the wholeprocess to manipulate stream and equipment thermodynamic conditions.

In the system 101 shown in FIG. 1, a C5 feedstock stream 103 comprisingn-pentane at, e.g., at least 50 wt % is combined with a hydrogenco-feedstock stream 105 to form a combined stream 107, which is thencombined with a recycle third C5-rich stream 109 to form a combined feedstream 111, which is fed to a first reactor 113 (also labeled R1). Themolar ratio of hydrogen to the C5 feedstock in stream 111 can range from0.1 to 3.0, preferably from 0.3 to 2.0, more preferably from 0.5 to 1.5.A major purpose of co-feeding hydrogen is to prevent coke formation onthe catalyst, especially at locations where the in-situ producedhydrogen is at a relatively low concentration. The reactor 113 may be afixed bed reactor with a bed of catalyst 115 loaded therein. Thecatalyst 115 is chosen from the compositions described above. Reactionsof the C5 hydrocarbons in the presence of the catalyst particles arehighly endothermic. Thus, reactor 113 is heated by external heating tomaintain an internal temperature in the range from 450° C. to 800° C.The weight hourly space velocity is in the range from 1 to 100 hour′. Asubstantial portion of the C5 hydrocarbons in the feed 111 is convertedinto CPD and byproducts such as acyclic diolefins, acyclic mono olefins,cyclopentane, cyclopentene; light components including hydrogen andC1-C4 hydrocarbons; one-ring aromatics; and multiple-ring aromatics at atotal conversion of n-pentane in the range from 50% to 99%. At theoutlet of the first reactor 113, a first reactor hydrocarbon effluent117 is drawn at a temperature in the range from 500 to 800° C. and at atotal absolute pressure in the range from 20 to 700 kilopascal absolute.

The first reactor hydrocarbon effluent 117 can comprise CPD at a totalconcentration in the range from 15 wt % to 80 wt %, on the basis of thetotal weight of C5 hydrocarbons in the first reactor hydrocarboneffluent 117. Once it exits the first reactor 113, the first reactorhydrocarbon effluent stream 117 is promptly cooled down by one or moreheat exchanger 119 to obtain a stream 121 to avoid undesired sidereactions such as thermal cracking, condensation of PNAs, and prematureDiels-Alder reactions of reactive diolefinic species, especially CPD. Aquantity of wash oil (not shown) may be added prior to and/or withinexchanger 191 to help prevent fouling.

The cooled stream 121 and a wash oil steam 125 are then fed into awashing vessel 123, where the first reactor hydrocarbon effluent isfurther quenched down to obtain a washed first reactor hydrocarboneffluent stream 129. The wash oil used in the example shown in FIGS. 1and 2 comprises alkylnaphthalene(s) and/or alkylbenzene at a totalconcentration of at least 50 wt %, although other wash oil as describedabove may be used.

Stream 129 comprises C5 components and light components from the firstreactor hydrocarbon effluent. Stream 129 may also contain C6, C7, C8,and the wash oil at non-negligible amounts. A wash oil bottom stream127, comprising the wash oil, one-ring aromatics and multiple-ringaromatics, is also obtained from the washing vessel 123.

The upper stream 129, as clean first reactor hydrocarbon effluent, isthen supplied to a first separation sub-system 131 (also labeled SD1),where a first C5-rich stream 133, one or more additional C5-rich streams134 (one shown in FIG. 1), and a light component stream 161 comprisinghydrogen and C1-C4 hydrocarbons are obtained. The C5-rich streams 133and 134 are advantageously depleted of C1-C4 hydrocarbons. Stream 133can comprise one or more of C6, C7, C8+, and the heavy wash oil atnon-negligible amounts. Stream 134 desirably comprises C6, C7, C8+, andthe heavy wash oil at significantly lower concentrations than stream133. Preferably, stream 134 is essentially free of C10+ and the heavywash oil. Stream 161 is fairly large in total volume, given the amountof hydrogen produced in the first reactor 113. To recover thenon-negligible amount of C5 components present in stream 161, stream 161is further contacted with a fresh solvent (sometimes such as the washoil) stream 165 and/or a recovered wash oil stream 168 in vessel 163(also called “debutanizer” or “debutanizer section”) to obtain a stream167 comprising H₂ and C1-C4 hydrocarbons and depleted of C5 components.The debutanizer bottom stream 125 exiting debutanizer vessel 163 is thenrecycled to the washing vessel 123 as described above. Stream 167 can befurther separated by using various equipment and processes (now shown),such as PSA, RCPSA, TSA, cryogenic method, and membrane separation, toobtain one or more of the following: (i) a high-purity H₂ stream; (ii) aH₂/C1-C4 hydrocarbon mixture stream; and (iii) a C1-C4-rich hydrocarbonstream.

Stream 133, to the extent it may comprise one or more of C6, toluene,C8+, and the wash oil at non-negligible concentration(s), is fed into aheavy wash oil (e.g., alkylnapthalene)-removal column 135 together withstream 127 described above, where an upper stream 137 rich in C5 anddepleted of C10+, and a lower stream 138 comprising C7 and C8+ areobtained. Stream 138 is then fed into distillation column 301, fromwhich an upper, wash oil-rich stream 305 and a lower stream 307 rich inheavy oil are obtained. Stream 305 (also labelled as stream 168) isrecycled to debutanizer vessel 163 (shown) (and/or partly or entirelyrecycled to washing vessel 123, not shown) described above forextracting residual C5 hydrocarbons from the light components-richstream 161. Lightly used wash oil stream 125 exiting debutanizer 163 isthen recycled to washing vessel 123. Efforts should be taken to reducereactions between CPD and acyclic diolefins in heat exchanger 191,vessels 123, 135, and the front end of the first separation sub-system131. Nonetheless, because such side reactions may take place at variousdegrees, it is highly desirable that column 135 is operated under acondition such that reverse dimerization reaction is favored overdimerization, such that heavy components such as DCPD, reaction productsbetween DCPD and acyclic diolefins are converted into CPD and other C5components, and therefore CPD and other C5 components that otherwisewould be lost to side reactions are at least partially recovered. Tothat end, the conditions in the column 135 comprise advantageously acolumn bottom temperature in the range from 150 to 350° C., preferablyfrom 170 to 260° C., and a total absolute pressure in the range from 3psia to 50 psia (21 to 345 kilopascal absolute), preferably from 20 psiato 40 psia (138 to 276 kilopascal absolute), and a residence time in therange from 0.01 to 10 hours, preferably from 0.1 to 4 hours.

Stream 137 and stream 134, both C5-rich and depleted of C10+, togetheras the first C5-rich fraction obtained from the first separationsub-system, is then delivered to the second reactor (also labeled R2,and called first dimerization reactor) 139 operating under a first setof dimerization conditions to convert a portion of the CPD containedtherein into DCPD. The first set of dimerization conditionsadvantageously comprise: a temperature in the range from 30 to 250° C.,preferably from 70 to 140° C., such as from 90 to 130° C., and a totalabsolute pressure in the range from 50 psia to 1000 psia (345 to 6895kilopascal absolute), preferably from 100 psia to 500 psia (689 to 3447kilopascal absolute), and a residence time in the range from 1 to 220minutes, preferably from 20 to 200 minutes, such as from 100 to 200minutes. Such conditions are optimized to favor the dimerizationreaction between CPD molecules and to minimize the reactions between CPDand other diolefins.

From the reactor 139, a second reactor effluent 141 comprising CPD,other C5 hydrocarbons, and DCPD is then fed into a second separationdevice 143 (SD2), which can be a distillation column. From column 143,an ultra high-purity DCPD lower stream 147 and an upper streamcomprising CPD and other C5 hydrocarbons are obtained. Stream 147 cancomprise DCPD at a concentration of at least 95 wt %, such as 96 wt %,98 wt %, 99 wt %, or even higher, based on the total weight of the C10hydrocarbons of the stream 147. Stream 147 may be purified in asubsequent distillation column (not shown) to obtain (1) an ultrahigh-purity DCPD, which comprises DCPD at a concentration of at least 95wt %, such as 96 wt %, 98 wt %, 99 wt %, or even higher, based on thetotal weight of the stream; (2) a light wash oil-rich stream, which canbe recycled to vessel 163 and/or washing vessel 123 described above (notshown) to further reduce the net import of fresh wash oil.

Upper stream 145, which is the second C5-rich fraction in the process ofthe present invention, is then fed into a second dimerization reactor(the third reactor of the present invention, R3) 149 operated under asecond set of dimerization conditions, where the remaining CPD in stream147 is partly converted into DCPD. The second set of dimerizationconditions advantageously comprise: a temperature in the range from 30to 250° C., preferably from 100 to 140° C., and a total absolutepressure in the range from 50 psia to 1000 psia (345 to 6895 kilopascalabsolute), preferably from 100 psia to 500 psia (689 to 3447 kilopascalabsolute), and a residence time in the range from 1 to 300 minutes,preferably from 150 to 300 minutes. Such conditions are optimized tomaximize recovery of the remaining CPD while achieving on-specproduction of a subsequent DCPD fraction.

From the reactor 149, a third reactor effluent 151 comprising CPD, otherC5 hydrocarbons, and DCPD is then fed into a third separation device 153(SD3), which can be a distillation column. From column 153, ahigh-purity DCPD lower stream 155 and an upper stream comprising CPD andother C5 hydrocarbons 157 are obtained. Stream 155 can comprise DCPD ata concentration of at least 90 wt %, such as 92 wt %, 94 wt %, 95 wt %,or even higher, based on the total weight of the C10 hydrocarbons of thestream 155. Stream 155 may be purified in a subsequent distillationcolumn (not shown) to obtain (1) a high-purity DCPD, which comprisesDCPD at a concentration of at least 90 wt %, such as 92 wt %, 94 wt %,95 wt %, or even higher, based on the total weight of the stream; (2) alight wash oil-rich stream, which can be recycled to vessel 163 and/orwashing vessel 123 described above (not shown) to further reduce the netimport of fresh wash oil.

DCPD streams 147 and 155 may be sold or delivered as products. The usermay convert these streams back into CPD or other compounds, depending onthe intended applications.

Upper stream 157, which is the third C5-rich fraction in the process ofthe present invention, can be fed into a third dimerization reactor (notshown), where the remaining CPD therein can be converted into anadditional amount of DCPD, which can be separated and recovered as athird DCPD-rich fraction in a fourth separation device (not shown), ifso desired. If a third dimerization reactor is utilized, the preferredmodes of operation for the first dimerization reactor and seconddimerization reactor can be advantageously adjusted for the purpose ofproducing DCPD products at optimal quality levels, each with optimalquantities. Typically, the third DCPD-rich fraction would have a lowerpurity than the first and second DCPD-rich fractions produced upstreamin the process as described above.

As shown in FIG. 1, the third C5-rich fraction stream 157 from the thirdseparation device 153 is divided into two streams 159 and 161. To theextent streams 157, 159 and 161 may comprise C6+ in addition to C5hydrocarbons, stream 161 is then separated in distillation column 163 toobtain a fifth C5-rich stream 165 that is depleted with C6+ and aC6-rich stream 167. Stream 165 can then be recycled to the first reactor113 (R1) as stream 109, as described above. Stream 167 may be purged orused in other applications, such as an untreated mogas component asdescribed below. It has been found that in this particular embodiment,without the distillation column 163, if the weight ratio of stream 161to stream 159 is higher than 0.4:0.6, accumulation of C6+ species mayoccur in the system. It is highly desired that stream 161 is subjectedto purification in column 163 before being recycled to the first reactorto eliminate such restriction on the recycle ratio.

Stream 159 (and, optionally, a portion of the first C5-rich fractionstream 137, and a portion of the second C5-rich fraction stream 145, notshown in FIG. 1) can be used for many purposes, due to the many usefulcomponents contained therein: CPD, cyclopentane, cyclopentene, pentene,pentadiene, 2-methylbutadiene, and the like.

For example, stream 159 (and other C5-rich fraction streams, and C6-richstream 167) can be partly or entirely converted into a mogas componentby selective hydrogenation to convert at least a portion of the dienestherein to mono olefins and/or saturates. The high concentrations ofcyclopentane and cyclopentene in stream 159 after hydrogenation makes itparticularly suitable for mogas blending due to the high octane andlower Reid Vapor Pressure values of cyclopentane and cyclopentenerelative to the starting feedstock of acyclic C5 hydrocarbon such asn-pentane. The C6-rich stream 167 may be used directly as a mogascomponent after selective hydrogenation as well.

For another example, before or after selective hydrogenation, stream 159(and other C5-rich fraction streams) may be separated to obtain at leastone pure stream of the following: cyclopentane, cyclopentene, pentene,1,3-pentadiene, 1,4-pentadiene, and 2-methylbutadiene.

FIG. 2 schematically illustrates an exemplary first separationsub-system 201 useful in the process and system of the presentinvention, particularly in the exemplary process illustrated in FIG. 1.The first separation sub-system 201 in FIG. 2 comprises a compressiontrain including multiple-stage compression, cooling and liquid/vaporseparation. In the process of this figure, the upper stream 129comprising a majority of washed first reactor effluent obtained fromcolumn 123 is first fed into a first-stage compressor 203, from which astream 205 at a higher pressure is obtained. Stream 205 is then cooledby a first-stage heat exchanger 207 to obtain a liquid/vapor mixturestream 209, which is fed into a first-stage liquid/vapor separationdevice (such as a drum) 211 to obtain a first-stage lower liquid stream215 comprising C5 hydrocarbons but depleted of hydrogen and C1-C4hydrocarbons and a first-stage upper vapor stream 213 comprising C5hydrocarbons and rich in hydrogen and C1-C4 hydrocarbons. Stream 213 isthen compressed by a second-stage compressor 217 to obtain a stream 219with an even higher pressure, which is then cooled by a second-stageheat exchanger 221 to obtain a second-stage lower temperatureliquid/vapor mixture stream 223, which is separated in a second-stageliquid/vapor separation device (such as a drum) 225 to obtain asecond-stage lower liquid stream 229 comprising C5 hydrocarbons butdepleted of hydrogen and C1-C4 hydrocarbons and a second-stage vaporstream 227 comprising C5 hydrocarbons and rich in hydrogen and C1-C4hydrocarbons. Stream 227 is then compressed by a third-stage compressor231 to obtain a stream 233 with an even higher pressure, which is thencooled by a third-stage heat exchanger 235 to obtain a lower temperaturethird-stage liquid/vapor mixture stream 237, which is separated in athird-stage liquid/vapor separation device (such as a drum) 239 toobtain a third-stage lower liquid stream 241 comprising C5 hydrocarbonsbut depleted of hydrogen and C1-C4 hydrocarbons and a third-stage uppervapor stream 161 comprising rich in hydrogen and C1-C4 hydrocarbons and,optionally, comprising C5 hydrocarbons at a lower concentration. Stream161 is then fed to a vessel 163 as illustrated in FIG. 1 and describedabove.

As shown in FIG. 2, stream 215, to the extent it may comprisenon-negligible concentrations of at least one of the wash oil, C7, andC8+(such as DCPD), can be fed into the heavy wash oil-removal column 135together with stream 127, where it is processed to obtain a C5-richstream 137 depleted with heavy wash oil as described above in connectionwith FIG. 1. Downstream streams 229 and 241, to the extent they tend tocomprise lower concentrations of the heavy wash oil, C7, and C8+, may becombined to form a single stream 134, which is then combined with stream137 as the first C5-rich fraction directly fed into the firstdimerization reactor 139 (R2) as illustrated in FIG. 1.

It is contemplated, though not shown, that streams 215, 229, and 241, tothe extent they may all contain non-negligible concentrations of atleast one of the heavy wash oil, C7, and C8+(such as DCPD), may be alldelivered to the heavy wash oil-removal column 135 along with stream127, where the C5-rich stream 137 is obtained and delivered to the firstdimerization reactor 139.

It is also contemplated, though not shown, that streams 215, 229, and241, to the extent they may all contain the heavywash oil, C7, and C8+at sufficiently low concentrations, if any at all, may be combined withstream 137 and then delivered directly to the first dimerization reactor139.

INDUSTRIAL APPLICABILITY

The first hydrocarbon reactor effluent obtained during the acyclic C₅conversion process containing cyclic, branched and linear C₅hydrocarbons and, optionally, containing any combination of hydrogen, C₄and lighter byproducts, or C₆ and heavier byproducts is a valuableproduct in and of itself. Preferably, CPD and/or DCPD may be separatedfrom the reactor effluent to obtain purified product streams which areuseful in the production of a variety of high value products.

For example, a purified product stream containing 50 wt % or greater, orpreferably 60 wt % or greater of DCPD is useful for producinghydrocarbon resins, unsaturated polyester resins, and epoxy materials. Apurified product stream containing 80 wt % or greater, or preferably 90wt % or greater of CPD is useful for producing Diels-Alder reactionproducts formed in accordance with the following reaction Scheme (I):

where R is a heteroatom or substituted heteroatom, substituted orunsubstituted C₁-C₅₀ hydrocarbyl radical (often a hydrocarbyl radicalcontaining double bonds), an aromatic radical, or any combinationthereof. Preferably, substituted radicals or groups contain one or moreelements from Groups 13-17, preferably from Groups 15 or 16, morepreferably nitrogen, oxygen, or sulfur. In addition to the monoolefinDiels-Alder reaction product depicted in Scheme (I), a purified productstream containing 80 wt % or greater, or preferably 90 wt % or greaterof CPD can be used to form Diels-Alder reaction products of CPD with oneor more of the following: another CPD molecule, conjugated dienes,acetylenes, allenes, disubstituted olefins, trisubstituted olefins,cyclic olefins and substituted versions of the foregoing. PreferredDiels-Alder reaction products include norbornene, ethylidene norbornene,substituted norbornenes (including oxygen containing norbornenes),norbornadienes, and tetracyclododecene, as illustrated in the followingstructures:

The foregoing Diels-Alder reaction products are useful for producingpolymers and copolymers of cyclic olefins copolymerized with olefinssuch as ethylene. The resulting cyclic olefin copolymer and cyclicolefin polymer products are useful in a variety of applications, e.g.,packaging film.

A purified product stream containing 99 wt % or greater of DCPD isuseful for producing DCPD polymers using, for example, ring openingmetathesis polymerization (ROMP) catalysts. The DCPD polymer productsare useful in forming articles, particularly molded parts, e.g., windturbine blades and automobile parts.

Additional components may also be separated from the reactor effluentand used in the formation of high value products. For example, separatedcyclopentene is useful for producing polycyclopentene, also known aspolypentenamer, as depicted in Scheme (II).

Separated cyclopentane is useful as a blowing agent and as a solvent.Linear and branched C₅ products are useful for conversion to higherolefins and alcohols. Cyclic and non cyclic C₅ products, optionallyafter hydrogenation, are useful as octane enhancers and transportationfuel blend components.

EXAMPLES

The following non-limiting examples 1-7 illustrate the invention.Examples 1-5 are obtained by using simulation. In these examples, therespective first reactor effluents are fed forward to the quench/washsection (123), a compression train section (SD1, 131), and adebutanization section (163) in similar manners as discussed above. Allthe recovered C5-rich fractions produced from the quench/wash section(135), the compression train section (SD1, 131), and debutanizationsection (163) are routed to the heavy wash oil-removal column (135), andsubsequently to a first dimerization reactor (R2, 139), an ultrahigh-purity DCPD recovery column (SD2, 143), a second dimerizationreactor (R3, 149), and then a high-purity DCPD recovery column (SD3,153).

Example 1

In this example, a first reactor effluent produced from pure n-pentanefeedstock, a pure hydrogen co-feedstock with 1:2 hydrogen/n-pentanemolar ratio, without co-feeding a light hydrocarbon or recycling of anydown-stream C5-rich fractions to the first reactor. The processtemperature, pressure, weight hourly space velocity, and molecularweight at the reactor inlet are 475° C., 62 psia (401.9 kilopascalabsolute), 15 hr⁻¹, and 49.01 g/mol, respectively. Temperature andpressure at the reactor outlet are 575° C. and 10 psia (68.9 kilopascalabsolute), respectively. The reactions generate an additional 1.87 molesof molecules in the first reactor effluent exiting the outlet per moleof molecules in the total feed material at the inlet. This 1.87-foldmolar expansion has the effects of lowering the molecular weight anddensity of the stream mixture from 49.01 g/mol at the inlet to 27.05g/mol at the outlet and from 3.08 kg/m³ at the inlet to 0.26 kg/m³ atthe outlet, respectively. The pressure drop from the inlet to the outletof the first reactor is calculated to be about 52 psi (359 kilopascal).Composition of the first reactor effluent at the outlet is given inTable I below.

The entire third C5-rich fraction is used as a mogas blend for makingmogas, the composition of the mogas blend is provided in Table I belowas well.

In this example, to produce 100 tons of CPD in stream 117, a totalweight of 403 tons of n-pentane feed is fed to the system (representinga total CPD yield of 24.8 wt %, based on all weight of the n-pentanefeed), a total weight of 13.1 tons of hydrogen is produced, a totalweight of 82 tons of UHP DCPD with purity level exceeding 99.0 wt %(stream 147) is produced, a total weight of 11 tons of DCPD with puritylevel exceeding 90.0 wt % (stream 155) is produced, and a total weightof 238 tons of mogas blend is produced.

Example 2

The reactor inlet and outlet temperature and pressure remain the same asin Example 1 above. However, in this example, a C5-rich stream, producedas 35% of the third C5-rich fraction obtained by separating the thirdreactor effluent produced from a second dimerization reactor describedabove, is recycled to the first reactor, where it is admixed withn-pentane before being fed into the first reactor. Hydrogen is co-fed atH₂/(all C5 hydrocarbons except (iso-C5 hydrocarbons and CPD)) molarratio of 1:2. It has been experimentally found that the reaction pathwayfrom iso-C5 hydrocarbons to CPD is kinetically inhibited under thereaction conditions. The composition of the total feed to the firstreactor is given in Table I below.

The remaining 65% of the third C5-rich fraction is used as a mogas blendfor making mogas. The composition of the mogas blend is provided inTable I below as well.

In this example, to produce 100 tons of CPD in stream 117, a totalweight of 308 tons of n-pentane feed is fed into the system(representing a CPD yield of 32.5 wt %, based on the total weight of then-pentane feed), a total weight of 11.7 tons of hydrogen is produced, atotal weight of 85 tons of UHP DCPD (stream 147) with purity levelexceeding 99.0 wt % is produced, a total weight of 8 tons of DCPD(stream 155) with purity level exceeding 90.0 wt % is produced, and atotal weight of 146 tons of mogas blend is produced.

To produce the same amount of CPD, Example 2 (with 35% recycle of thethird C5-rich fraction to the first reactor) requires 23.4% less offresh n-pentane feed than Example 1 (without recycle of any of theC5-rich fraction to the first reactor).

To produce the same amount of CPD, Example 2 produces 10.8% less ofhydrogen than Example 1, due to using partially unsaturated feed versusa fully saturated feed. This has the benefit of reduced volumetric flowrates in the reactor(s) and downstream equipment. For example, the firstreactor in Example 2 shows a 7.8% reduction in volumetric flow than inExample 1. This may have significant impacts on the equipment sizing ofthe downstream quench tower(s), gas compressor(s), and debutanizer(s).

The enthalpy changes of the stream across the first reactor also showssignificant reduction in Example 2 compared to Example 1. Thistranslates into a 10.9% reduction in furnace firing in Example 2, whichcan have a significant impact of the equipment sizing of the reactor(s)and fuel costs. The amount of heat required for sustaining theendothermic reactions in the first reactor is comparatively lower whenusing a partially converted C5 feedstock.

To produce 100 tons of CPD, Example 2 shows a 38.6 wt % of reduction ofmaterials diverted to mogas production. Furthermore, it can be seen fromTable I that the mogas stream in Example 2 has a slightly higher octanevalue of C5+ byproduct than in Example 1 since more kinetically limitedisomerization and aromatization products will be concentrated into asmaller byproduct stream.

Thus, clearly, it may be advantageous to recycle at least part of theC5-containing streams to the CPD reactor(s). This is especiallybeneficial if demand for the partially converted C5 hydrocarbons arereduced, e.g., during certain seasons when the RVP spec on mogas limitsthe amount of C5 hydrocarbons that can be blended. This allows the plantto continue to operate at desired DCPD product rates with lowerquantities of co-products.

TABLE I Composition of First Total Feed Reactor Hydrocarbon Compositionof Composition (wt %) Effluent at Exit (wt %) Mogas Blend (wt %) ExampleExample Example Component 1 2 1 2 1 2 Hydrogen 1.30 1.30 4.51 4.28 — —Methane 0.00 0.00 1.50 1.34 — — Ethylene 0.00 0.00 0.11 0.10 — — Ethane0.00 0.01 0.97 0.87 — — Propylene 0.00 0.04 0.73 0.70 0.04 0.07 Propane0.00 0.06 0.75 0.72 0.05 0.08 Isobutane 0.00 0.00 0.00 0.00 0.00 0.00Isobutylene 0.00 0.03 0.14 0.16 0.03 0.05 1-butene 0.00 0.18 0.73 0.820.14 0.27 1,3-butadiene 0.00 0.05 0.19 0.22 0.04 0.07 n-butane 0.00 0.220.79 0.93 0.17 0.33 t-2-butene 0.00 0.23 0.80 0.94 0.18 0.35 c-2-butene0.00 0.18 0.58 0.70 0.13 0.27 3-methyl-1-butene 0.00 0.02 0.05 0.06 0.010.03 1,4-pentadiene 0.00 0.02 0.05 0.05 0.01 0.02 Isopentane 0.00 0.100.22 0.30 0.06 0.14 1-pentene 0.00 1.28 3.99 3.98 1.19 1.952-methyl-1-butene 0.00 0.09 0.19 0.26 0.06 0.13 Isoprene 0.00 0.02 0.060.08 0.01 0.03 n-pentane 98.70 88.73 32.64 30.87 9.81 15.27  t-2-pentene0.00 2.51 7.72 7.67 2.34 3.81 c-2-pentene 0.00 1.41 4.35 4.31 1.32 2.142-methyl-2-butene 0.00 0.15 0.33 0.46 0.10 0.23 CPD 0.00 0.17 24.5125.57 0.08 0.25 t-1,3-pentadiene 0.00 0.91 2.78 2.81 0.82 1.38c-1,3-pentadiene 0.00 0.74 2.28 2.32 0.67 1.12 Cyclopentene 0.00 1.143.43 3.51 1.03 1.73 Cyclopentane 0.00 0.18 0.56 0.56 0.17 0.27 Benzene0.00 0.25 0.72 0.89 0.19 0.37 Toluene 0.00 0.00 0.00 0.00 — —Meta-xylene 0.00 0.00 0.00 0.00 — — DCPD 0.00 0.00 0.00 0.00 — —Di-isoprene 0.00 0.00 0.00 0.00 — — Naphthalene 0.00 0.00 2.45 2.55 — —Methylnaphthalene 0.00 0.00 0.00 0.00 — — Anthracene 0.00 0.00 1.70 1.77— — Pyrene 0.00 0.00 0.19 0.20 — — TOTAL 100.00 100.00 100.00 100.00100.00  100.00 

Example 3

In this prophetic example, obtained by simulation, a model third C5-richfraction used as the mogas blend and a corresponding partiallyhydrogenated mogas component having the following compositions in TableII can be obtained:

TABLE II Concentration in (wt %) Post-Selective Components Third C5-richFraction Hydrogenation Propylene 0.22 0.22 Propane 0.27 0.27 Isobutane0.00 0.00 Isobutylene 0.14 0.14 1-butene 0.75 0.81 1,3-butadiene 0.210.00 n-butane 0.91 0.91 t-2-butene 0.95 1.01 c-2-butene 0.72 0.793-methyl-1-butene 0.07 0.07 1,4-pentadiene 0.07 0.00 Isopentane 0.340.34 1-pentene 6.36 9.11 2-methyl-1-butene 0.30 0.32 Isoprene 0.05 0.00n-pentane 52.59 52.59 t-2-pentene 12.54 15.21 c-2-pentene 7.08 9.752-methyl-2-butene 0.54 0.56 Cyclopentadiene 0.44 0.00 t-1,3-pentadiene4.41 0.00 c-1,3-pentadiene 3.61 0.00 Cyclopentene 5.54 5.98 Cyclopentane0.90 0.90 Benzene 1.01 1.01 C10 (dimers) 0.00 0.00 Total 100.00 100.00

Example 4

In this example, a first reactor effluent produced from pure n-pentanefeedstock, a pure hydrogen co-feedstock with 1:1 hydrogen/n-pentanemolar ratio, without co-feeding a light hydrocarbon or recycling of anydown-stream C5-rich fractions to the first reactor. The processtemperature, pressure, weight hourly space velocity, and molecularweight at the reactor inlet are 475° C., 62 psia (401.9 kilopascalabsolute), a lower weight hourly space velocity than Example 1 to attaina closer approach to thermodynamic equilibrium, and 49.01 g/mol,respectively. Temperature and pressure at the reactor outlet are 575° C.and 10 psia (68.9 kilopascal absolute), respectively. In this example,the reaction system also employs a different catalyst system fromExample 1. The reactions generate an additional 2.02 moles of moleculesin the first reactor effluent exiting the outlet per mole of moleculesin the total feed material at the inlet. This 2.02-fold molar expansionhas the effects of lowering the molecular weight and density of thestream mixture from 36.72 g/mol at the inlet to 18.16 g/mol at theoutlet and from 2.44 kg/m³ at the inlet to 0.18 kg/m³ at the outlet,respectively. The pressure drop from the inlet to the outlet of thefirst reactor is calculated to be about 52 psi (359 kilopascal).Composition of the first reactor effluent at the outlet is given inTable III below.

The entire third C5-rich fraction is used as a mogas blend for makingmogas, the composition of the mogas blend is provided in Table III belowas well.

In this example, to produce 100 tons of CPD in stream 117, a totalweight of 222 tons of n-pentane feed is fed to the system (representinga total CPD yield of 45.0 wt %, based on all weight of the n-pentanefeed), a total weight of 18.3 tons of hydrogen is produced, a totalweight of 54 tons of UHP DCPD with purity level exceeding 99.0 wt %(stream 147) is produced, a total weight of 44 tons of DCPD with puritylevel exceeding 90.0 wt % (stream 155) is produced, and a total weightof 77 tons of mogas blend is produced.

In this example, toluene is used as wash oil. Net import of toluene isestimated to be no more than 7 tons due to effective wash oil recyclebuilt into the process. Without recycling, net import of toluene wouldincrease to 251 tons on a once-through basis. This may have significantimpacts on the overall process economic viability.

TABLE III Composition Total Feed Composition of First of CompositionReactor Hydrocarbon Mogas Blend Component (wt %) Effluent at Exit (wt %)(wt %) Hydrogen 2.78 8.01 — Methane 0.00 2.02 0.01 Ethylene 0.00 0.11 —Ethane 0.00 2.42 0.05 Propylene 0.00 0.98 0.13 Propane 0.00 2.29 0.38Isobutane 0.00 0.04 0.03 Isobutylene 0.00 0.23 0.17 1-butene 0.00 0.710.53 1,3-butadiene 0.00 0.04 0.03 n-butane 0.00 1.63 1.72 t-2-butene0.00 0.81 0.90 c-2-butene 0.00 0.62 0.79 3-methyl-1-butene 0.00 0.240.60 1,4-pentadiene 0.00 0.14 0.38 Isopentane 0.00 0.54 1.46 1-pentene0.00 1.69 4.62 2-methyl-1-butene 0.00 0.93 2.55 Isoprene 0.00 0.43 1.10n-pentane 97.23 5.35 14.33 t-2-pentene 0.00 4.14 11.37 c-2-pentene 0.002.10 5.78 2-methyl-2-butene 0.00 1.49 4.09 CPD 0.00 43.76 1.97t-1,3-pentadiene 0.00 1.13 2.96 c-1,3-pentadiene 0.00 0.93 2.43Cyclopentene 0.00 12.21 32.99 Cyclopentane 0.00 3.13 7.97 Benzene 0.000.48 0.01 Toluene 0.00 0.38 — Meta-xylene 0.00 0.04 — DCPD 0.00 0.00 —Di-isoprene 0.00 0.00 — Naphthalene 0.00 0.87 — Methylnaphthalene 0.000.07 — Anthracene 0.00 0.01 — Pyrene 0.00 0.00 — TOTAL 100.00 100.00100.00

Example 5

In this prophetic example, obtained by simulation, a model third C5-richfraction used as the mogas blend and a corresponding partiallyhydrogenated mogas component having the following compositions in TableIV can be obtained:

TABLE IV Concentration in (wt %) Post-Selective Components Third C5-richFraction Hydrogenation Propylene 0.13 0.08 Propane 0.38 0.26 Isobutane0.03 0.02 Isobutylene 0.17 0.15 1-butene 0.53 0.49 1,3-butadiene 0.030.00 n-butane 1.72 1.53 t-2-butene 0.90 0.81 c-2-butene 0.79 0.713-methyl-1-butene 0.60 0.57 1,4-pentadiene 0.38 0.00 Isopentane 1.461.43 1-pentene 4.62 4.93 2-methyl-1-butene 2.55 3.07 Isoprene 1.10 0.00n-pentane 14.33 14.30 t-2-pentene 11.37 14.41 c-2-pentene 5.78 8.292-methyl-2-butene 4.09 4.64 Cyclopentadiene 1.97 0.08 t-1,3-pentadiene2.96 0.00 c-1,3-pentadiene 2.43 0.00 Cyclopentene 32.99 35.52Cyclopentane 7.97 8.14 Benzene 0.01 0.01 C10 (dimers) 0.00 0.00 Total100.00 100.00

Example 6—ZSM-5 Catalyst Composition Synthesis

A synthesis mixture with ˜20.3% solids was prepared from 10,000 g ofdeionized (DI) water, 600 g of 50% NaOH solution, 25 g of 45% SodiumAluminate solution, 730 g of n-propyl amine 100% solution, 80 g of ZSM-5seed crystals, and 3,190 g of Ultrasil PM™. Modified silica were mixedin a 5-gal pail container and then charged into a 5-gal autoclave aftermixing. The synthesis mixture had the following molar composition:

-   -   SiO₂/Al₂O₃˜470    -   H₂O/SiO₂˜12.1    -   OH/SiO₂˜0.16    -   Na/SiO₂˜0.16    -   n-PA/Si˜0.25.

The synthesis mixture was mixed and reacted at 230° F. (110° C.) at 250rpm for 72 hours. The resulting product was filtered and washed with DIwater and then dried in the oven at ˜250° F. (121° C.) overnight. Aportion of the as-synthesized crystals were converted (forcharacterization) into the hydrogen form by three ion exchanges withammonium nitrate solution at room temperature, followed by drying at250° F. (121° C.) and calcination at 1000° F. (540° C.) for 6 hours. Theresulting ZSM-5 crystals had a SiO2/Al₂O₃ molar ratio of ˜414, totalsurface area (SA)/(micropore SA+mesopore SA) of 490 (440+51) m²/g,Hexane sorption of 117 mg/g and an Alpha value (as measured on theproton form) of 31. A second portion of the material was used assynthesized for Pt impregnation.

ZSM-5 having a SiO₂/Al₂O₃ molar ratio of 414 and a sodium content of0.38 wt % was calcined for 6 hours in nitrogen at 900° F. (482° C.).After cooling, the sample was reheated to 900° F. (482° C.) in nitrogenand held for three hours. The atmosphere was then gradually changed to1.1, 2.1, 4.2, and 8.4% oxygen in four stepwise increments. Each stepwas held for 30 minutes. The temperature was increased to 1000° F. (540°C.), the oxygen content was increased to 16.8%, and the material washeld at 1000° F. (540° C.) for 6 hours. After cooling, 0.5 wt % Pt wasadded via incipient wetness impregnation using an aqueous solution oftetraamine platinum hydroxide. The catalyst composition was dried in airat room temperature for 2 hours, then at 250° F. (121° C.) for 4 hours,and lastly calcined in air at 660° F. (349° C.) for 3 hours. Thecatalyst composition powder was pressed (15 ton), crushed, and sieved toobtain 20-40 mesh particle size.

Example 7—Catalyst Composition Performance Evaluation

The above material of Example 6 was evaluated for performance. Thecatalyst composition (0.5 g) was physically mixed with quartz (1.5 g,60-80 mesh) and loaded into a reactor. The catalyst composition wasdried for 1 hour under He (100 mL/min, 30 psig (207 kPa), 250° C.) thenreduced for 1 hour under H₂ (200 mL/min, 30 psig (207 kPa), 500° C.).The catalyst composition was then tested for performance with feed ofn-pentane, H₂, and balance He, typically at 550° C.-600° C., 5.0 psia(35 kPa-a) C₅H₁₂, 1.0 molar H₂:C₅H₁₂, 14.7 WHSV, and 30 psig (207 kPa)total. Catalyst composition stability and regenerability was tested postinitial tests at 550° C. to 600° C. by treatment with H₂ (200 mL/min, 30psig (207 kPa), 650° C.) for 5 hours, then retesting performance at 600°C.

Cyclopentadiene and three equivalents of hydrogen are produced bydehydrogenation and cyclization of n-pentane (Equation 1). This isachieved by flowing n-pentane over a solid-state, Pt containing catalystcomposition at elevated temperature. The performance ofZSM-5(414:1)/0.5% Pt of Example 6 was evaluated based on n-pentaneconversion, cyclic C₅ production (cC5), cracking yields, and stability.These results are summarized in Table V, Table VI, Table VII, and TableVIII.

$\begin{matrix}{{C_{5}H_{12}}\overset{\Delta}{\rightarrow}{{C_{5}H_{6}} + {3\; H_{2}}}} & {{Equation}\mspace{14mu}(1)}\end{matrix}$

TABLE V Temperature Conversion (%) Selectivity (mol %) Yield (mol %) (°C.) C5H12 cC5 CPD C1 C2-4 iC5 cC5 CPD C1 C2-4 iC5 cC5:C1-4 545 71 33 2011 21 4.4 24 14 8.1 15 3.1 1.0 570 80 37 26 13 22 3.7 30 21 10 17 3.01.1 595 84 40 32 13 22 3.1 34 26 11 18 2.6 1.1 595, Post H2 76 38 30 1622 2.4 29 23 12 17 1.8 1.0

TABLE VI Temperature Conversion (%) Selectivity (mol %) Yield (mol %) (°C.) C5H12 iC5 iC5o iC5= iC5== iC5 iC5o iC5= iC5== 545 71 4.4 1.1 3.20.04 3.1 0.8 2.3 0.03 570 80 3.7 0.8 2.8 0.05 3.0 0.7 2.3 0.04 595 843.1 0.7 2.4 0.05 2.6 0.6 2.0 0.05 595, Post H2 76 2.4 0.6 1.8 0.04 1.80.5 1.4 0.03

TABLE VII Temperature Conversion (%) Selectivity (C %) Yield (C %) (°C.) C5H12 cC5 CPD C1 C2-4 iC5 cC5 CPD C1 C2-4 iC5 cC5:C1-4 545 71 40 242.8 15 5.3 28 17 2.0 11 3.7 2.2 570 80 45 32 3.1 16 4.5 36 26 2.5 13 3.62.3 595 84 50 39 3.3 16 3.8 42 33 2.8 14 3.2 2.5 595, Post H2 76 48 384.1 17 3.0 37 29 3.1 13 2.3 2.3

TABLE VIII Temperature Conversion (%) Selectivity (C %) Yield (C %) (°C.) C5H12 iC5 iC5o iC5= iC5== iC5 iC5o iC5= iC5== 545 71 5.3 1.4 3.80.05 3.7 1.0 2.7 0.04 570 80 4.5 1.0 3.5 0.06 3.6 0.8 2.8 0.04 595 843.8 0.8 2.9 0.07 3.2 0.7 2.5 0.06 595, Post H2 76 3.0 0.8 2.2 0.05 2.30.6 1.7 0.03

Table V and Table VII show the conversion of n-pentane and selectivityand yield of cyclic C₅, CPD, iso-C₅, C₁, and C₂₋₄ cracking products atvarying temperatures (average values over 8 hours at each temperature)for a catalyst composition of 0.5 g ZSM-5(Si:Al₂ molar ratio 414:1)/0.5wt % Pt at conditions of 5.0 psia (35 kPa-a) C₅H₁₂, 1:1 molar H₂:C₅,14.7 WHSV, 45 psia (310 kPa-a) total. In Table V, the selectivities andyields are expressed on a molar percentage basis for the respectivecyclic C5, CPD, iso-C5, C1, and C2-4 of hydrocarbons formed; i.e., themolar selectivity is the moles of the respective cyclic C₅, CPD, C₁, andC₂₋₄ formed divided by total moles of pentane converted. In Table VII,the selectivities and yields are expressed on a carbon percentage basisfor the respective cyclic C5, CPD, iso-C5, C1, and C2-4 of hydrocarbonsformed; i.e., the carbon selectivity is the moles carbon in therespective cyclic C5, CPD, iso-C5, C1, and C2-4 formed divided by totalmoles of carbon in the pentane converted. As can be seen, Table V andTable VII show greater than 80% conversion of pentane, at high WHSV, and40% selectivity to cyclic C5 species at 595° C. While not the specificend product, cyclopentane and cyclopentene can be recycled to produceCPD.

Tables VI and VIII further specify the individual iC5 components whichare shown as totals in Tables V and VII. iC5o is iso pentane; including2-methyl butane and 3-methyl butane. iC5=is isopentenes including2-methyl butene and 3-methyl butene. iC5==is iso-pentadienes; including2-methyl butadiene and 3-methyl butadiene. These results show the lowlevels of iso-pentadienes that are possible with the example catalyst.

All documents described herein are incorporated by reference herein,including any priority documents and/or testing procedures to the extentthey are not inconsistent with this text. As is apparent from theforegoing general description and the specific embodiments, while formsof the invention have been illustrated and described, variousmodifications can be made without departing from the spirit and scope ofthe invention. Accordingly, it is not intended that the invention belimited thereby. Likewise, the term “comprising” is consideredsynonymous with the term “including.” Likewise, whenever a composition,an element or a group of elements is preceded with the transitionalphrase “comprising,” it is understood that we also contemplate the samecomposition or group of elements with transitional phrases “consistingessentially of,” “consisting of,” “selected from the group of consistingof,” or “is” preceding the recitation of the composition element, orelements and vice versa.

What is claimed is:
 1. A process for making cyclopentadiene (CPD) andoptionally dicyclopentadiene (DCPD), the process comprising: (I) feedinga C5 feedstock comprising at least one acyclic C5 hydrocarbon into afirst reactor; (II) contacting the at least one acyclic C5 hydrocarbonwith a catalyst under conversion conditions to obtain a first reactorhydrocarbon effluent comprising: C5 components including CPD and acyclicdiolefins; light components including hydrogen and C1-C4 hydrocarbons;one-ring aromatics; and multiple-ring aromatics; (III) contacting thefirst reactor hydrocarbon effluent with a wash oil in a washing vessel,thereby obtaining: a heavy stream comprising at least a portion of thewash oil and at least a portion of the multiple-ring aromatics; and awashed first reactor hydrocarbon effluent comprising at least a portionof the light components, at least a portion of the C5 components, and,optionally, a portion of the wash oil but depleted in multiple ringaromatics; (IV) separating the washed first reactor effluent in a firstseparation sub-system to obtain: a first C5-rich fraction comprising CPDand depleted of the light components; a first light components-richfraction comprising hydrogen and C1-C4 hydrocarbons; and an optionalfirst recovered wash oil stream; (V) supplying the heavy stream and,optionally, at least a portion of the optional first recovered wash oilstream to a wash oil recovery sub-system; (VI) obtaining, from the washoil recovery sub-system: a heavy oil fraction comprising themultiple-ring aromatics; a second recovered wash oil stream; and anoptional recovered C5-rich stream comprising CPD; and (VII) recycling atleast a portion of the second recovered wash oil stream, and,optionally, at least a portion of the optional first recovered wash oilstream directly or indirectly to the washing vessel.
 2. The process ofclaim 1, wherein the wash oil recovery sub-system comprises at least onedistillation column operated at least partly under wash oil recoveryconditions such that DCPD, if present in the wash oil recoverysub-system, at least partly undergoes retro-Diels-Alder reaction toproduce CPD.
 3. The process of claim 1, wherein: the wash oil recoverysub-system comprises a first wash oil distillation column and a secondwash oil distillation column; in step (V), at least a portion of theheavy stream and the optional first recovered wash oil stream aresupplied to the first wash oil distillation column; and step (VI)comprises: (VIa) obtaining from the first wash oil distillation columnan upper stream comprising recovered C5 hydrocarbons as the recoveredC5-rich stream, and a lower stream comprising the wash oil and themultiple-ring aromatics; (VIb) supplying at least a portion of the lowerstream into the second wash oil distillation column; and (VIc) obtainingfrom the second wash oil distillation column: the heavy oil fractioncomprising at least a portion of the multiple-ring aromatics; and thesecond recovered wash oil stream.
 4. The process of claim 3, wherein aflux oil is added to the first wash oil distillation column, the secondwash oil distillation column, and/or the heavy oil fraction.
 5. Theprocess of claim 1, wherein: the wash oil recovery sub-system comprisesa first wash oil divided-wall distillation column; in step (V), at leasta portion of the heavy stream and the optional first recovered wash oilstream are supplied to the first wash oil divided-wall distillationcolumn; and step (VI) comprises: (VIa) obtaining from the first wash oildivided-wall distillation column: an upper stream comprising recoveredC5 hydrocarbons as the recovered C5-rich stream, a middle streamcomprising the recovered wash oil as the second recovered wash oilstream, and a lower stream comprising the heavy oil fraction comprisingat least a portion of the multiple-ring aromatics.
 6. The process ofclaim 5, wherein a flux oil is added the first wash oil divided-walldistillation column and/or the heavy oil fraction.
 7. The process ofclaim 3, wherein the wash oil recovery sub-system is operated at leastpartly under wash oil recovery conditions such that dicyclopentadiene(DCPD), if present in the wash oil recovery sub-system, at least partlyundergoes retro-Diels-Alder reaction to produce CPD.
 8. The process ofclaim 2, wherein: the heavy stream and/or the optional first recoveredwash oil stream comprises DCPD; the second recovered wash oil streamcomprises CPD; and the heavy oil fraction is essentially free of DCPD;such as less than 10 wt % DCPD.
 9. The process of claim 1, furthercomprising: (VIII) feeding at least a portion of the second recoveredwash oil stream and the first light components-rich fraction into athird light components separation device; (IX) obtaining from the thirdseparation device: a second light components-rich fraction comprisinghydrogen and C1-C4 hydrocarbons depleted in C5+ hydrocarbons, and athird wash oil stream; and (X) recycling at least a portion of the thirdwash oil stream to the washing vessel in step (III).
 10. The process ofclaim 1, further comprising feeding a fresh stream of wash oil into atleast one of (i) the washing vessel and (ii) the third separationdevice.
 11. The process of claim 1, further comprising: (XI) supplyingat least a portion of the first C5-rich fraction and, optionally, theoptional recovered C5-rich stream into a second reactor operating undera first set of dimerization conditions; (XII) obtaining a second reactoreffluent from the second reactor comprising CPD and DCPD; and (XIII)separating at least a portion of the second reactor effluent to obtain:a first DCPD-rich fraction comprising DCPD; and a second C5-richfraction.
 12. The process of claim 11, further comprising: (XIV) feedingat least a portion of the second C5-rich fraction into a third reactoroperating under a second set of dimerization conditions; (XV) obtaininga third reactor effluent from the third reactor comprising CPD and DCPD;and (XVI) separating at least a portion of the third reactor effluent toobtain: a second DCPD-rich fraction; and a third C5-rich stream.
 13. Theprocess of claim 11, further comprising: (XVII) feeding at least aportion of the third C5-rich fraction into a fourth reactor operatingunder a third set of dimerization conditions; (XVIII) obtaining a fourthreactor effluent from the fourth reactor comprising CPD and DCPD; and(XIX) separating at least a portion of the fourth reactor effluent in afourth separation device to obtain: a third DCPD-rich fraction; and afourth C5-rich stream.
 14. The process of claim 11, further comprising:(XX) supplying at least a portion of at least one of the following intoa fifth separation device: (i) the first C5-rich stream; (ii) theoptional recovered C5-rich stream; (iii) the second C5-rich stream; (iv)the third C5-rich stream, if any; (v) the fourth C5-rich stream, if any;and (XXI) obtaining, from the fourth separation device: a fifth C5-richstream; and a one-ring aromatic(s)-rich stream.
 15. The process of claim14, further comprising: (X) recycling at least a portion of the one-ringaromatic(s)-rich stream directly or indirectly into the washing vesselin step (III) and/or the third separation device in step (VIII).
 16. Theprocess of claim 14, wherein at least a portion of the one-ringaromatic(s)-rich stream is distilled to obtain a benzene-rich stream anda benzene-depleted stream and the benzene depleted stream is feddirectly to at least one of (i) the washing vessel in step (III) and/or(ii) the third separation device in step (VIII).
 17. The process ofclaim 1, wherein the first separation sub-system comprises a compressiontrain with inter-stage cooling and vapor/liquid separation.
 18. Theprocess of claim 1, wherein the wash oil comprises at least one of:cylcohexane; monoalkyl, dialkyl, and trialkyl cyclohexanes; benzene;monoalkyl, dialkyl, and trialkyl benzenes; monoalkyl, dialkyl, trialkyl,and tetraalkyl naphthalenes; other alkylated multiple-ring aromatics;and mixtures and combinations thereof.
 19. The process of claim 18,wherein: the wash oil comprises at least 50 wt % of toluene, based onthe total weight of the wash oil used in step (III).
 20. The process ofclaim 18, wherein: the wash oil comprises at least 50 wt % ofalklynaphthalenes, based on the total weight of the wash oil used instep (III); and the optional first recovered wash oil stream is obtainedin step (IV).
 21. The process of claim 1, wherein: the first reactorhydrocarbon effluent comprises CPD at a concentration of C(CPD)1 wt %and acyclic diolefins at a total concentration of C(ADO)1 wt %, bothbased on the total weight of C5 hydrocarbons in the first reactorhydrocarbon effluent; and C(CPD)1/C(ADO)1≧1.5.
 22. The process of claim1, wherein: step (IV) comprises: (IVc) obtaining from the first lightcomponents-rich fraction to obtain at least one of: (i) a hydrogen-richstream comprising H₂ at a purity of at least 95 mol %; (ii) ahydrogen/C1-C4 hydrocarbon stream comprising a mixture of H₂ and C1-C4hydrocarbon; and (iii) a C1-C4 hydrocarbon stream depleted of hydrogen.23. The process of claim 11, further comprising: (XXIII) recycling,directly or indirectly, at least a portion of at least one of the firstC5-rich fraction, the optional recovered C5-rich stream, the secondC5-rich fraction, the third C5-rich fraction, the fourth C5-richfraction, and/or the fifth C5-rich fraction, if produced, to the firstreactor.
 24. The process of claim 11, further comprising: (XXIV)obtaining at least one of: (i) a cyclopentane-rich fraction; (ii) acyclopentene-rich fraction; (iii) a 1,3-pentadiene-rich fraction; and(iv) a 2-methyl-1,3-butadiene fraction, from at least one of the firstC5-rich fraction, the optional recovered C5-rich stream, the secondC5-rich fraction, the third C5-rich fraction, and the fourth C5-richfraction, and the fifth C5-rich fraction, if produced.